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Geant4 User's Guide - For Toolkit Developers June 28, 2005

1. PtrSolid G4Transform3D from global HEDI rect Transform Eo 1 oo G4VSolid from management 1 fshapeName G4String G4VSolid G4GRSSolid from volumes G4GRSSolid WV G4VSolid G4ThreeVector from global G4RotationMaty from global ix G4GRSVolume from volumes G4GRSVolume fhistory G4VPhysicalVolume Gy fname G4String G4NavigationHistory from volumes lt lt const gt gt GetName Figure 20 10 Touchables 94 BackLevel c4NavigationHistory lt lt const gt gt GetDepth lt lt const gt gt GetTopTransform lt lt const gt gt GetTopVolume G4VTouchable G4GRSSolid G4GRSVolume G4TouchableHistory from volume from volumes from volumes A A A X X X G4GRSSolidHandle GaGRSVolumeHandle G4TouchableHistoryHandle from volumes from volumes from volumes G4TouchableHandle V IT Ass zXG4ReferenceCountedHandle from global Figure 20 11 Reference counting for touchables 95 G4SmartVoxelProxy G4SmartVoxelProxy
2. eee ee AR LA END Ww gimme a vertex ji from TrackManagement O Sa gimmesecondlaries n ut Sue j ne gimme Trajectory V E Se processOneTrack Yrs y A Te ON ji af G UserTrajectony gt 1 Nou i ej PR T AS 4 as d G Track NS ecce uj x m d UE MN xxn J iS a C M U pay Bc li j P x m Pa X u EN EN 2 ARCU Pres Ne 4 y Ped YN a TR s G4DynamicParticle _ _G4Traject iy 5 uid y GALA actor GADynamicFa ici j from ParticleDefinition from TrackManagemerit from EventGenerator amar ian xwann d Pe za Day RL fae C from TrackManagement from PhysiesProcess fe l bs E NES Ya TX N ES V Cm Y ZA GEE i uS AOR ae SE Medes d Nasen File users asai g4 v_0830 mdi Thu Aug 31 14 00 49 1995 Class Diagram EventManagement Main Figure 4 1 Event gleton and should be constructed by G4RunManager e G4VPrimaryGenerator the abstract base class of all of primary generators This class has only one pure virtual method GeneratePri mary Vertex which takes a G4Event object generates a primary ver tex and associates primary particles with the vertex Booch diagrams for classes related to the event and event generator classes are shown in Figs 4 1 and
3. G4Particle gt 2 P i t Inserti G4Dynamic GALorentz y Definition parent ye brt Ky Particle IN Rotation as Me 0 n tirom Globals nee ES j i P parent EN I N hannel FTU y EAR P S channels GavDecayChe G4Allocator ve poe M E er did a fi K ee G4VDecayChannel o er jTP Secum Globale ts G4DecayProducts Fa ERE ana Fi G4DecayChannel Pann LN GetParentParticle GotBR Fa Vector f RWTPtrSor i Boost GetParent PushProducts GetDaughter IsChecked 7 a y UN Ns i ps i bs n GaDecayProducls a CONI rcu Wik P ListElement G4MuonDecayChannel aye next GADecayProductsListEl ment lan dase y Decayit GP hase paca D co j epoca E Decayit Pd from PhysicsProcess S 1 Sei OneBodyDecayl Decaylt Se TwoBodyDecayit gt and many others s cake e ThreeBodyDecaylt __ L T i yA ManyBodyDecaylt Figure 10 3 Particle Decay Table 39 Chapter 11 Materials 11 1 Design Philosophy The design of the materials category reflects what exists in nature materials are made of a single element or a mixture of elements and elements are made of a single isotope or a mixture of isotopes Because the physical properties of materials can be described in a generic way by quantities which can be specified directly such as density or derived from the element composition only concrete classes
4. Figure 8 1 Overview of the geometry 34 Chapter 9 Electromagnetic Fields The object oriented design of the classes related to the electromagnetic field is shown in the class diagram of Fig 9 1 The diagram is described in UML notation 35 fDetectorFi avigator entFieldMgr Figure 9 1 Electromagnetic Field 36 Chapter 10 Particles 10 1 Design Philosophy The particles category implements the facilities necessary to describe the physical properties of particles for the simulation of particle matter interac tions All particles are based on the G4ParticleDefinition class which de scribes basic properties such as mass charge etc and also allows the particle to carry a list of processes to which it is sensitive A first level extension of this class defines the interface for particles that carry cuts information for ex ample range cut versus energy cut equivalence A set of virtual intermediate classes for leptons bosons mesons baryons etc allows the implementation of concrete particle classes which define the actual particle properties and in particular implement the actual range versus energy cuts equivalence All concrete particle classes are instantiated as singletons to ensure that all physics processes refer to the same particle properties 10 2 Class Design The object oriented design of the particles related classes is shown in the following class diagrams The diagrams are descri
5. classA and should be wriiten by the ses f 1 auther of classA a E qme PS command N Ne A e guidance N eae P N messenger 0 1 MR X POR Sa 7 y mae ae F G4Ulparameter G4Ulcommand a TT sheckNenvatwety 4 7 ec NO aly list n gt getCurrentValue o n defaultValue G4String y list ee omittable G4bool commandGuidance G4String 8 Parameter ET parameterGuidance G49ring commandName G4String parameterName G4String eommandPath G4String parameterRange G4String i Il parameterType char l i je pee pre p Figure 14 1 Overview of intercom classes 14 3 Status of this section 27 06 05 design philosophy from Geant4 general paper and class design sec tions added by D H Wright 53 Part ILI Extending Toolkit Functionality Chapter 15 Geometry 15 1 What can be extended GEANT4 already allows a user to describe any desired solid and to use it in a detector description in some cases however the user may want or need to extend GEANT4 s geometry One reason can be that some methods and types in the geometry are general and the user can utilise specialised knowledge about his or her geometry to gain a speedup The most evident case where this can happen is when a particular type of solid is a key element for a specific detector geometry and an investment in improving i
6. access function that creates on requests a polyhedron and stores it for future access and should be customised for every solid The method GANURBS CreateNURBS const is not currently utilised so you do not have to implement it 59 would fit 15 3 Modifying the Navigator For the vast majority of use cases it is not indeed necessary and definitely not advised to extend or modify the existing classes for navigation in the geometry A possible use case for which this may apply is for the description of a new kind of physical volume to be integrated We believe that our set of choices for creating physical volumes is varied enough for nearly all needs Future extensions of the GEANT4 toolkit will probably make easier exchang ing or extending the G4Navigator by introducing an abstraction level sim plifying the customisation At this time a simple abstraction level of the navigator is provided by allowing overloading of the relevant functionalities Extending the Navigator The main responsibilities of the Navigator are e locate a point in the tree of the geometrical volumes e compute the length a particle can travel from a point in a certain direction before encountering a volume boundary The Navigator utilises one helper class for each type of physical volume that exists You will have to reuse the helper classes provided in the base Navigator or create new ones for the new type of physical volume To extend G4Navigator
7. 22 G4ProcessManager P EndTracking D GetAlongStepProcessVector G4ProcessAttr 2 GetAtRestProcessVector RE n GetPostStepProcessVector GetProcessList G4ProcessAttr SetProcessActivation i tg Vector StartTracking FERE G4PhysicsVector Bus 9 9 C ATP e luca Ens UT Sick iom is Pa RWTPtrOrdered gt ibute Vector G4ProcessAttribute E isActive G4bool aos from RWTools idxProcessList G4it B as EM idxProcVector G4int theProbessList theProtVector S j 7 i E 7 ordProcVector Gdint VEL Ta a nllo QU 3 RWTPtrOrdered aProcess G4VProcess T r Vector Y soup e ED Tre from EwToots i RWIValOrdered 7 ES ek G4VProcess Vector ARA K ptrNextTable Trom RWToois AD V j GA4RWTProcess gt a RO Pal Vector d S m N Q4PhysicsVector s T c B 5 N GetValue A ji PutValue t on 7 P aatavectar j G4ParticleChange 7 Me from Track 1 Initialize Me AddSecondary M Clear N _ SetStatusChange G PhysicsLinear GaphysicsLog SetMomentumChange Vector r d Vector Ri GetLocalEnergyDeposit j amp kw TA E and others with secondaries aParibleQhange I V E Y 4 arbitrary binning PCR dE c G4VProcess A
8. GaStackedTrack 6 x j G4EventManager 7 Gap 5 Z e oopewsisi mE OneE from Dig Di erek an av n Track Gain T rS BekPrimaries0 C Males from OODBMS_Interface M stackSecondaries J summar ot EN Bnoerae CH wackContaier e stackS d ra rae see eee aes G Bool P N aa n di P da E PS eT x M i Nen EO M Geen PE x T a ud Por a G4Visualization hs x SS as zz track elector 11 stackedTrack N it N trackSefector re i om from Visualisation drawTrajectory gt n initiaizeEvent p dd PR P x LER P d i Ki Sw d es 4 GaStackedTrack G4TrackSelecto GA4TrajectoryCo priority Weight G4doubl 4 calc Weight ntainer initialWeight ishNewTrajsctonyi P N S p S EON amp pushNew rajectory ATAN Be weightThreshold jh c a Cer S e ector Y P NE primaryGenerator a el A pes e NY 527 Kem N es rom Bestia EJ v E T bos T 1 trajectorySelector a j N TES L m GaUsecTradic 7 J GA4TrajectorySelect Selector 1 v or s i A ToBeDrawn x se EE Hr a ps oBeStore pt G4EventGenerator gis Liz Ne 8S X a track md fromEvenGeneraton GATrackingManager iw trajectory generate one event
9. I Stegun Handbook of mathematical functions DOVER Publications INC New York 1965 chapters 9 10 and 22 45 Just one of the following Random Engines at a time 3 EMAIL HEN is active a gt HepJamesRandom default HepRandomEngine DRand48Engine RandEngine RanluxEngine M f RanecuEngine Ser Ww PNE G i Lu 2 setSeed long ya 1 setTheEngine i kn theEngine RandGauss 2 4 flat 2 d theGenerator 7 flat mera NA 10 flat Pi RandBreit WM 3 flat 7 T i pci rj 0 8a A Sho Wigner 5 shoot 7 7e aGenerator N tett e HepRandom ge 15 flat 6 is 0 S OW uU p RandPoisson Dem AU N P D a 8 shoot gp YAS 14 shoot Se 12 flat _ SG x 9 flat M VRAT RandExpon Re ential Ah Figure 12 2 Shooting via the generator ONS UN C t localEngine y Talat Pe Pose NOL wz flat ene me flat PoissonDi stribution M A ca 2 fire 2 n Be _ 4 FiaiDistrib fire BWDistribu ution tion J Ce GaussDist a ution ribution TN rd Ms _ J zx E kur Figure 12 3 Shooting via distribution objects HEPGeometry Documentation for the HEPGeometry module is provided in the CLHEP Reference Guide http cern ch wwwasd lhc 4
10. are provided G4V3DNucleus and G4VScatterer At this point in time the usage of these intra nuclear transport related classes by concrete codes is not enforced by designs as the details of the cascade loop are still model de pendent and more experience has to be gathered to achieve standardisation It is within the responsibility of the implementers of concrete intra nuclear transport codes to use the abstract interfaces as defined in these classes The class diagram is shown in figure 18 6 for the string parton model aspects and in figure 18 7 for the intra nuclear transport 18 Framework functionality Again variants of Strategy Bridge and Chain of Responsibility are used G4VPartonStringModel implements the initial isation of a three dimensional model of a nucleus and the logic of scatter ing It delegates secondary production to string fragmentation through a G4VStringFragmentation pointer It provides a registering service for the concrete string fragmentation and delegates the string excitation to derived classes Selection of string excitation is through selection of derived class Selection of string fragmentation is through registration 18 7 Level 5 Framework String De excitation G4 Excited String Gamin SestPos tion pem EE eG etPartonL 1h j ideo eee SG st4vierentum GV SiningFragmertabon SreetPaton SrragrentStina STransfomToCenta amisa j j ALonAong2 A kerat SGostHad oni Cong eba S G4 Exci
11. detector It is well suited to the hierarchical approach The hierarchical design manages the complexity of the tracking category by separating the 11 system into layers Each layer may then be designed independently of the others In order to maintain high performance tracking use of the inheritance is a relation hierarchy in the tracking category was avoided as much as possible For example track and particle classes might have been designed so that a track is a particle In this scheme however whenever a track object is used time is spent copying the data from the particle object into the track object Adopting the aggregation has a relation hierarchy requires only pointers to be copied thus providing a performance advantage 5 2 Class Design Fig not yet available shows a general overview of the tracking design in Unified Modelling Language Notation e G4TrackingManager is an interface between the event and track cat egories and the tracking category It handles the message passing between the upper hierarchical object which is the event manager G4EventManager and lower hierarchical objects in the tracking cate gory G4TrackingManager is responsible for processing one track which it receives from the event manager G4TrackingManager aggregates the pointers to G4SteppingManager G4Trajectory and G4UserTrackingAction It also has a use relation to G4Track e G4SteppingManager plays an essential role in
12. e RandPoisson distribution class defining Poisson random number distribution given a mean It also provides a method to fill an array of flat random values given its size Fig 12 2 is a dynamic object diagram illustrating the situation when a single random number is thrown by the static generator according to one of the available distributions Only one engine is assumed to active at a time Fig 12 3 illustrates a random number being thrown by explicitly specify ing an engine which can be shared by many distribution objects The static interface is skipped here Fig 12 4 illustrates the situation when many generators are defined each by a distribution and an engine The static interface is skipped here For detailed documentation about the HEPRandom classes see the CLHEP Reference Guide http cern ch wwwasd lIhc clhep manual RefGuide index html or the CLHEP User Manual http cern ch wwwasd lhc clhep manual UserGuide index html Informations written in this manual are extracted from the original manifesto distributed with the HEPRandom package http cern ch wwwasd geant geant4_public Random html 44 pn MT flat nr wA DhRand48Engie flatArray _RanluxEngine p gt ZARE gt n RT setSeed IQ ox flat flatArray d Sy setSeeds 2 flatArray setSeed X m do setSeed San E Re setSeeds Y i Nd E setSeeds lesane d ko O deese Y 4 HepJamesRandom MC M NI T E WAA
13. s flat Ji esee w 2 flatArray m lv Fa HepRandomEngine RanecuEngine setSeed D Ma 7 Wa A flat setSeeds j SSS flatArray C flatArray n 0 7 getSeed MEE NSS setSeed 2 n 07 ia s getSeeds f setSeeds setSeed setSeeds 1 0 o 3 QW yaki theEhgine ra Dena EET zu HepRandom flat flatArray getTheEngine getTheGenerator getTheSeed getTheSeeds getTheTableSeeds setTheEngine setTheSeed setTheSeeds 1 RandFlat y EL rd fire M Saz edu r KWE A Ei RandEoisson irelni N P ire shoot x shoot shootArray Se shootArray shooln Jus N SR fireArray 1 to ny vs MO et earn N en 07 UU Fae P RandGauss rx C ET 2 BandExponential shoot RandBreitWigner sd O shootArray Hor fire MOAN fireArray d shoot 0 n ip ic shootArray fireArray j ran ku fireArray ton e On j Figure 12 1 HEPRandom module HEPNumerics The HEPNumerics module includes a set of classes which implement numerical algorithms for general use in GEANTA Section 3 2 3 of the User s Guide for Application Developers contains a description of each class Most of the algorithms were implemented using methods from the following books e B H Flowers An introduction to Numerical Methods In C Clare don Press Oxford 1995 e M Abramowitz
14. Int NAE ade ee amii P zt wt a E O1 T asco e GaHCtablek b TUE CN a G4SteppingMan ement tre Top S ager X N See from Tracking MP LA ARE KE NNE RA G4SDStructure gt G4LogicalVolume manager caGWat y from Geometry N i addNewDetector getSD p Fe P initialize i x9 terminate 7j Te A 27 ME oe 7 c ES wes detector SensitiVeDetector __ x P E FOR dik G4VSensitiveDetector PAL G4Step PA activate from Tracking x clear Rane drawAll J Em endOfEvent 4 getCollectionName i getName e aGolleetion getPathName E Pon D km A get_numberOfCollections G4VReadOut y TR Geometry 7 Sw deAcive 0 N A G4EventManage ear r _ ticom EveniManagemet _ _ G dEvent from EventManagement add hitsCollection 7 get HCofThisEvent H s 44 2 AHCofThisEvent add_hitsCollection get HC get_capacity y 7 get numberOfCollections E et ES He event RS G4VHitsCollection SDname G4String SDpathName G4String lt collectionName G4String E d M4 printAll processHits GaVHit ian draw print Figure 7 1 Overview of hit classes management G4V Digitizer
15. K K K K K K K K K K KK 14 2 Class De i l 2 5 A ura Q Sk ha ad utm ee arse eod 14 3 Status of this section os uus inm x 3 9 Xo Go Ae K K K K III Extending Toolkit Functionality 15 Geometry 15 1 What can be extended KK KI K KI K K K K K K K KK 15 2 Adding a new type of Solid 15 3 Modifying the Navigator K K K K K K K K K K KK 16 Electromagnetic Fields 16 1 Creating a New Type of Field ls 16 2 Status of this chapter ue K K K K K K aa ae te ards 17 Physics Processes 17 1 Status of this chapter K K K K K K K K K K K K K 18 Hadronic Physics 18 1 Pn rod ue UOTE dca Je ied e ob Mn ee Sah ee PR dur 18 2 Principal Considerations lle 18 3 Level 1 Framework processes cles 18 4 Level 2 Framework Cross Sections and Models 18 5 Level 3 Framework Theoretical Models 18 6 Level 4 Frameworks String Parton Models and Intra Nuclear Cascades ED c ravra 18 7 Level 5 Framework String De excitation 19 Visualization IV Appendix 20 Class Diagrams for the Geometry Category Part I Introduction Chapter 1 Introduction 1 1 Scope of this manual The User s Guide for Toolkit Developers provides detailed information about the design of Geant4 classes as well as the information required to extend the current functionality of the Geant4
16. OO design of the physical volume Figure 20 3 shows the OO design of the CSG solids Figure 20 4 shows the OO design of the boolean solids Figure 20 5 shows the OO design of the specific solids Figure 20 6 shows the OO design of the BREP solids Figure 20 7 shows the OO design of the BREP curves Figure 20 8 shows the OO design of the BREP surfaces Figure 20 9 shows the OO design for reflections of solids Figure 20 10 shows the OO design of the touchables Figure 20 11 shows the OO design of reference counting of touchables Figure 20 12 shows the OO design of smart voxels Figure 20 13 shows the OO design of the navigator Figure 20 14 shows the OO design of detector regions 84 G4VSo1id fMateri G4Material from materijas G4LogicalVolumeStore lt lt static gt gt DeRegister S static GetInstance lt lt static gt gt Register G4FieldManager from magneticfiel G4VPhysicalVolume 1l ji l flog cal G4PhysicalVolumeList 1 from G4LogicalVolwme fD au rss 1 0 G4VSensitiveDetector fSensitiveDetectar from digits thits fVoxel 0 leasmartVoxelHeaddr fUserLimiXs d G4UserLimits from global Figure 20 1 Logical volumes 85 G4LogicalVolume amp fName G4String addDaughter lt lt const gt gt Ge
17. WG stCutsrRadius sTyps GavPariclescatterer dae GsthudeorRadiln n GaPatdsT ps aGernmeTorteradien 1 Paa Pinopki m35 G6thudearRodua Ha L Seat ndFragrens DoLerant Benab AreYeLHI0 antc Track SOcLorantz Boost T mnsStsep DoLerertz Contraction iDeLerertz Contractionn y SpoTrareiatian G4ParideScatiere 4 Start op t G4 Fidd Propagaton AG st lsxtiluclsonc aZrer e erm r j amp tAmahudsora Tram perti tied keze han n MI GetE xdtahorEnergy Sint I G4Fancy3DNudeus Figure 18 7 Level 4 implementation framework of the hadronic category of GEANT4 intra nuclear transport aspect 1 Allow to select string decay algorithm 2 Allow to select string excitation 3 Allow the selection of concrete implementations of three dimensional models of the nucleus 4 Allow the selection of concrete implementations of final state and cross sections in intra nuclear scattering Design and interfaces To fulfil the requirements on string models two abstract classes are provided the G4VPartonStringModel and the G4VString Fragmentation The base class for parton string models GAVPartonStringModel declares the GetStrings pure virtual method G4VStringFragmentation the pure abstract base class for string fragmentation declares the interface for string fragmentation To fulfill the requirements on intra nuclear transport two abstract classes
18. Yoursel SSatMinEneray x 0 ___ SSetMaxEnerayt a aa m DeActivaleFor J GAMaterial lt Concete gt gt ConcreteM odel C Figure 18 3 Level 2 implementation framework of the hadronic category of GEANT4 final state production aspect 71 lt Abatract gt gt G4HadronicP roce ss Paavia gt gt Gethicroscopie Cross Section gt gt PostStspOo b 0 lt lt Conerets gt Purely Abalrart gt gt G4 lso ParlicleChange G4V EotopsProdudion WGet k ctepac lt lt Corc ste G4Heutronlsoiope Production Figure 18 4 Level 2 implementation framework of the hadronic category of GEANT4 isotope production aspect senting an object that encapsulates methods and data for calculating total cross sections for a given process in a certain range of validity The im plementations may take any form It can be a simple equation as well as sophisticated parameterisations or evaluated data All cross section data set classes are derived from the abstract class G4VCrossSectionDataSet which declares methods that allow the process inquire about the applicabil ity of an individual data set through IsApplicable const G4DynamicParticle const G4Element and to delegate the calculation of the actual cross section value through GetCrossSection const G4DynamicParticle const G4Element Final state production The G4HadronicInteraction base class is pro vided for final state generation It decl
19. a pure virtual DeExcite method for further evolution of the system when intra nuclear transport as sumptions break down DeExcite takes a G4Fragment the GEANT4 repre sentation of an excited nucleus as argument The base class for evaporation phases GAVExcitationHandler declares an abstract method BreakItUP for compound decay Framework functionality The G4TheoFSGenerator class inherits from G4HadronicInteraction and hence can be registered as a model for final state production with a hadronic process It allows a concrete implementa tion of G4VIntranuclearTransportModel and G4VHighEnergyGenerator to be registered and delegates initial interactions and intra nuclear transport of the corresponding secondaries to the respective classes The design is a complex variant of a Strategy The most spectacular application of this pat tern is the use of parton string models for string excitation quark molecular dynamics for correlated string decay and quantum molecular dynamics for transport a combination which promises to result in a coherent description of quark gluon plasma in high energy nucleus nucleus interactions The class G4VIntranuclearTransportModel provides registering mech anisms for concrete implementations of GAVPreCompoundModel and pro vides concrete intra nuclear transports with the possibility of delegating pre compound decay to these models G4VPreCompoundModel provides a registering mechanism for compound decay throug
20. area is expected 80 Bibliography 1 The GEANT 4 Collaboration CERN DRDC 94 29 DRDC P58 1994 2 E Gamm et al Design Patterns Addison Wesley Professional Com puting Series 1995 3 http cern ch wwwasd geant4 G4UsersDocuments Overview html index html 4 Kaidalov A B Ter Martirosyan K A Phys Lett B117 247 1982 5 Data Formats and Procedures for the Evaluated Nuclear Data File National Nuclear Data Center Brookhave National Laboratory Upton NY USA 6 For example VUU and R QMD model of high energy heavy ion col lisions H Stocker et al Nucl Phys A538 53c 64c 1992 7 P V Degtyarenko M V Kossov H P Wellisch Eur Phys J A 8 217 222 2000 8 VNI 3 1 Klaus Geiger Brookhaven BNL 63762 Comput Phys Commun 104 70 160 1997 9 M Bertini L L nnblad T Sj rstrand Pythia version 7 0 0 a proof of concept version LU TP 00 23 hep ph 0006152 May 2000 81 Chapter 19 Visualization The following sections contain various information for extending class func tionalities of GEANT4 visualization e User s Guide for Application Developers Chapter 8 Visualization e User s Guide for Toolkit Developers Chapter 3 Object oriented Anal ysis and Design of GEANT4 Classes Section 9 Visualization 82 Part IV Appendix Chapter 20 Class Diagrams for the Geometry Category Figure 20 1 shows the OO design of the logical volume Figure 20 2 shows the
21. experimental run is an event An event consists of a set of primary particles produced in an interaction and a set of detector responses to these particles In GEANT4 objects of the G4Event class are the primary units of a simulation run Before the event is processed it contains primary vertices and primary particles produced by an external physics generator After the event is processed it may also contain hits digitizations and optionally trajectories generated by the simulation The event category manages events and provides an abstract interface to external physics generators G4 Event and its content vertices and particles are independent of other classes This isolation allows GEANT4 based simulation programs to be in dependent of specific choices for physics generators and of specific solutions for storing the Monte Carlo truth G4Event avoids keeping any transient information which is not meaningful after event processing is complete Thus the user can store objects of this class for processing further down the pro gram chain For performance reasons G4 Event and its content classes are not persistent Instead the user must provide the transient to persistent con version 4 2 Class Design e G4Event This class represents an event It is constructed and deleted by G4RunManager or its derived class e GA4EventManager This class controls an event It must be a sin Dak S pr VERA LLL SK WAN TN
22. manager Energy loss information necessary for the Cherenkov process is passed using G4Step or the static dE dX table is used together with the step length information in G4Step to obtain the energy loss information Any other 5 6 Status of this chapter created by 10 06 02 partially re written by D H Wright 14 11 02 updated and partially re written by P Arce 19 Bibliography 1 Geant4 Users Guide for Application Developers 20 Chapter 6 Physics Processes 6 1 Design Philosophy The processes category contains the implementations of particle transporta tion and physical interactions All physics process conform to the basic interface G4VProcess but different approaches have been developed for the detailed design of each sub category For the decay sub category the decays of all long lived unstable particles are handled by a single process This process gets the step length from the mean life of the particle The generation of decay products requires a knowledge of the branching ratios and or data distributions stored in the particle class The electromagnetic sub category is divided further into the following packages e standard handling basic properties for electron positron photon and hadron interactions e low energy providing alternative models extended down to lower en ergies than the standard package e muons handling muon interactions e x rays providing specific code for x ray physics e opti
23. only made perpendicular to the cartesian axes G4RotationMatrixStore a container for optionally storing created G4Rotation Matrices G4SolidStore a container for optionally storing created solids It enables traversal of all any solids by the UI user etc The class is a singleton GAV Solid position independent geometrical entities They have only shape and encompass both CSG and boundary representations They are optionally entered into the G4SolidStore This class defines but does not implement functions to compute distances to from the shape Functions are also defined to check whether a point is inside the shape to return the surface normal of the shape at a given point and to compute the extent of the shape G4VSweptSolid a solid created by performing a 3D transformation on a finite planar face G4HalfSpaceSolid a solid created by the boolean AND of one or more half space surfaces G4BREPSolid a solid created by an abitrary set of finite surfaces G4V Touchable a class that maintains a reference on a given touchable element of the detector a kind of bookmark It enables a given detector element to be saved during tracking in case of booleans user code etc and the corresponding G4PhysicalVolume retrieved later with its state information path through the tree optionally restored so that navigation can be restarted G4Touchables provide fast access to the transformation from the global reference
24. particle tracking It per forms message passing to objects in all categories related to particle transport such as geometry and physics processes Its public method SteppingO steers the stepping of the particle The algorithm em ployed in this method is basically the same as that in Geant3 The GEANT4 implementation however relies on the inheritance hierarchy of the physics interactions The hierarchical design of the physics in teractions enables the stepping manager to handle them as abstract objects Hence the manager is not concerned with concrete interac tion objects such as bremsstrahlung or pair creation The actual in vocations of various interactions during the stepping are done through a dynamic binding mechanism This mechanism shields the tracking category from any change in the design of the physics process classes including the addition or subtraction of new processes G4SteppingManager also aggregates 12 the pointers to G4Navigator from the geometry category to the current G4Track and the list of secondaries from the current track through a G4TrackVector to G4UserSteppingAction and to G4VSteppingVerbose It also has a use relation to G4ProcessManager and G4ParticleChange in the physics processes class category e G4Track the class G4Track represents a particle which is pushed by G4SteppingManager It holds information required for stepping a par ticle for example the current position the time si
25. s 4re oen K K K K K K K K KEK IK KI 1 2 Class DOS OT ster durata ar QA Tot amp BT ole Seg Sana S e mte Goan Statu s f this chapters e acu a SWE dex we rae da e 8 Geometry 8 1 Design Philosopy KK KE KEK K K K KI K K E Es 8 25 Class DOSIPILU ue vnb Roe enb EE Sue DA Su eS S 8 3 Status of this chapter s uunc Rr K K K K K K K K KK 9 Electromagnetic Fields 10 Particles 10 1 Design Philosophy K K K K K pe K K K K K E 10 2 Clas8DeSig l c s awk A law Ie Sp ee uan dala Qu ek RC 10 3 Status of this chapter KII K K K K ws K K K K 11 Materials 11 1 Design Philosophy 4 qeu 4 KI oe BO K K K K K K KK 11 2 Glass Desio a ne owe xb Ro A RADA ok d deii 11 3 Status of this chapter ze gab Rr a E 12 Global Usage 12 1 Design Philosophy K K K K K ROBO rut IPSO cd ra FD x ran Kanal T m 12 3 Status of this chapter oeste ve K K e gestae K K K K 13 Visualization 13 1 Design Philosophy K K K K K K K K K K K K K K 13rd Clase eset S lt lt Ahaa ES 3A 2 oe Ahan JA Ay eG ANE us 13 3 Modeling sub category KK K KI een 13 4 View parameters 4 99 KI K K v 9 979 X 9 3 K K K KK 13 5 Status of this section amp 6x heo Bo K K K K K K K 21 21 22 22 22 25 25 25 28 29 29 30 33 35 14 Intercoms 14 1 Design Philosophy K K K
26. system to that of the saved detector element 32 e G4TouchableHistory object representing a touchable detector el ement and its history in the geomtrical hierarchy including its net resultant local global transform e G4GRSSolid object representing a touchable solid It maintains the association between a solid and its net resultant local to global transform e GAGRS Volume object representing a touchable detector element It maintains associations between a physical volume and its net resultant local to global transform e G4TransformStore a container for optionally storing created G4Affine Transform objects It is responsible for storing and providing access to transfor mations that are constant at tracking time e G4AffineTransform a class for geometric affine transformations It supports efficient arbitrary rotation and transformation of vectors and the computation of compound and inverse transformations A rotation flag is maintained internally for greater computational efficiency for transforms that do not involve rotation e G4UserLimits responsible for user limits on step size ascribable to individual volumes Fig 8 1 shows a general overview in UML notation of the geometry design A detailed collection of class diagrams from the geometry category is found in the Appendix 8 3 Status of this chapter 27 06 05 subsection on design philosphy from Geant4 general paper added by D H Wright 33
27. the path taken through the geometrical hierarchy It is principally a utility class for use by G4Navigator e G4NormalNavigation a utility class for navigation in volumes con taining only GAPVPlacement daughter volumes e G4ParameterisedNavigation a utility class for navigation in vol umes containing a single G4PVParameterised volume for which voxels for the replicated volumes have been constructed 30 G4VoxelNavigation a utility class for navigation in volumes con taining only G4PVPlacement daughter volumes for which voxels have been constructed G4ReplicaNavigation a utility class for navigation in volumes con taining a single G4PVParameterised volume for which voxels for the replicated volumes have been constructed G4PhysicalVolumeStore a container for optionally storing created physical volumes It enables traversal of all physical volumes by the Ul user etc All solids should be registered with G4PhysicalVolumeStore and removed on their destruction It is intended principally for the UI browser G4VPhysicalVolume a volume positioned within and relative to a given mother volume and also represented by a given logical volume They are optionally entered into the G4PhysicalVolumeStore G4PVPlacement a physical volume corresponding to a single touch able detector element positioned within and relative to a mother vol ume GAP V Indexed volume able to perform simple changes to its shape corresponds to
28. toolkit This manual is designed to e provide a repository of information for those who want to understand or refer to the detailed design of the toolkit and e provide details and procedures for extending the functionality of the toolkit so that experienced users may contribute code which is consis tent with the overall design of Geant4 This manual is intended for developers and experienced users of Geant4 It is assumed that the reader is already familiar with functionality of the Geant4 toolkit as explained in the User s Guide For Application Devel opers and also has a working knowledge of programming using C A knowledge of object oriented analysis and design will also be useful in un derstanding this manual It is also useful to consult the Software Reference Manual which provides a list of Geant4 classes and their major methods Detailed discussions of the physics included in Geant4 are provided in the Physics Reference Manual 1 2 How to use this manual To understand the goal of the software design of Geant4 it is useful to be gin by reading the User Requirements Document referred to in this chapter Chapter 2 Design and Function of the Geant4 Categories provides detailed information about the design of each class category and the classes in it Before considering an extension of one of the toolkit categories a de tailed understanding of that category is required Chapter 3 Extending Toolk
29. which describes how to visualize the corresponding component object belonging to a 3D scene G4ModelingParameters defines various associated parameters 50 For example G4PhysicalVolumeModel knows how to visualize a physical volume It describes a physical volume and its daughters to any desired depth G4HitsModel knows how to visualize hits G4TrajectoriesModel knows how to visualize trajectories G4FlavoredParallelWorld knows how to visualize flavoured parallel world volumes The main task of a model is to describe itself to a 3D scene by giving a concrete implementation of the following virtual method of G4VModel virtual void DescribeYourselfTo G4VGraphicsScene amp 0 The argument class G4VGraphicsScene is a minimal abstract interface of a 3D scene for the GEANT4 kernel defined in the graphics_reps cate gory Since G4VSceneHandler and its concrete descendants inherit from G4VGraphicsScene the method DescribeYourselfTo can pass information of a 3D scene to a visualization driver It is easy for a toolkit developer of GEANT4 to add a new kind of visual izable component object It is done by implementing a new class inheriting from G4V Model 13 4 View parameters View parameters such as camera parameters drawing styles wireframe surface etc are held by G4ViewParameters Each viewer holds a view parameters object which can be changed interactively and a default object for use in the vis viewer reset command If a toolki
30. 4 2 respectively 4 3 Status of this chapter 27 06 05 design philosophy section added from Geant4 general paper by D H Wright VA C zt p n e j G4EventGenerator A addGenerator 25 generateOneEvent i gimmeVertex i eh N ae Ssg G4OrderedV TN P4 ector PE from BaseClass pu p H P E gh we Pi N v generators EN N M E fo 1 n Ser ut N SSN i X B AS G4Dynami adil basi N G4PrimaryVertex 3 G wane icle y Fa Sene APER ven BA Sarl ade Yr a Y 1 from PhysicsProcess PE he vertex particles A insert e aea Net ot See Sed i N j G4UserPrimaryGen NWS s ae PA erator P d p E T dH A A ca m See z E f j na Hew 2 TEMO C m NA i PA TES S 4 w E E NE G4ParticleDefinition y G4DynamicParti y G4ParticleGun T gt from ParticleDefinition lt from ParticleDefinition Ki set particle definition DE e d set particle energy SA 1 fi Ssa set particle momentum set particle position PNE Sc d n SC Rae H d 7 d p I File users kurasige ROSE2 g40831 mdl Thu Aug 31 19 58 30 1995 Class Diagram EventGenerator Main Figure 4 2 Event Generator 10 Chapter 5 Tracking The tracking category manages the contribution of the processes to the evo lution of a track s state and provides informa
31. 4int theProcessManager _ __Manager_ GetMomentumDirection _ thePartisleBefin t n from PhysicsProcess C GetTotalEnergy 3 Sune u GetPolarization 1 i Le N 1 ek Po Soeur S PN SEA thePartisleTable 7 tnePreassionedQecayProducts theDecayTable u PM l 0 1 e REC eee theMemersmDirerion c NP i aH LiG4ParticleTable Aus Ww _ GADecayProducts G ADecayTable gt i GaParticle PushProducs SelecihDecayChannel y EN t amp Momentum 4 SetParentPartcle r insert H ae Uu Boost ES i JE re p x S j TE Figure 10 1 Particle classes 10 3 Status of this chapter 27 06 05 section on design philosophy added from Geant4 general paper by D H Wright 38 G4ParticleTable _ G4ParlicleMessenger P entries Z i setNewValue PA findParticle e g getCurrentValue findAntiParticle EN 1 5 Sag insert EZ GetParticleTable i N fDictionary N T n gt x erator NOM G4Strinc pu GAPTbIDictio G4PTbleDi o n G4Particle gt 4 narylterator ctionary i 1 Definition y AP ve eK _ RWTPtrSlis i SAAN Ee om Foal rom RWTook Figure 10 2 Particle Table Pa G4DecayTable i REND P ec EEN pA SelectADecayChannel s
32. All framework functional requirements were obtained through use case anal ysis In the following we present for each framework level the compressed use cases requirements designs including the flexibility provided and illus trate the framework functionality with examples All design patterns cited are to be read as defined in 2 18 3 Level 1 Framework processes There are two principal use cases of the level 1 framework A user will want to choose the processes used for his particular simulation run and a physicist will want to write code for processes of his own and use these together with the rest of the system in a seamless manner Requirements 1 Provide a standard interface to be used by process implementations 2 Provide registration mechanisms for processes Design and interfaces Both requirements are implemented in a sub set of the tracking physics interface in GEANT4 The class diagram is shown in figure 18 1 All processes have a common base class G4VProcess from which a set of specialised classes are derived Three of them are used as base classes for hadronic processes for particles at rest G4VRestProcess for interac tions in flight G4VDiscreteProcess and for processes like radioactive de cay where the same implementation can represent both these extreme cases G4VRestDiscreteProcess Each of these classes declares two types of methods one for calculating the time to interaction or the physical interaction le
33. G4cscsolid 87 Figure 20 3 CSG solids G4VSolid from management fshapeName G4String lt lt virtual gt gt CalculateExtent G4CSGSolid S virtual ComputeDimensions S virtual CreatePolyhedron lt lt virtual gt gt DistanceToIn lt lt virtual gt gt DistanceToOut lt lt virtual gt gt Inside lt lt virtual gt gt SurfaceNormal f PtnSolidB PtrSolidA j 1 g G4BooleanSolid lt lt virtual gt gt GetConstitue Figure 20 4 Boolean solids 88 G4VSo1id from management fshapeName G4String G4CSGSolid gt gt lt lt virtual gt gt ComputeDimensi lt lt virtual gt gt DistanceToIn lt lt virtual gt gt DistanceToOut lt lt const gt gt GetName lt lt virtual gt gt Inside G4VCSGfaceted Qofaces G4VCSGface Figure 20 5 Specific solids 89 G4Assembly lt lt const gt gt GetNumberOfSoli p lt lt const gt gt GetPlacedSolid e 1 placedVec G4PlacedSolid jt G4PlacedVector lt lt const gt gt GetRotation lt lt const gt gt GetSolid lt lt const gt gt GetTranslati G4IntersectionSolid from Geometry Boo Figure 20 6 BREP solids 90
34. GSPOSP and representing a single touchable detector element GAP VReplica a physical volume representing many identically formed touchable detector elements differing only in their positioning The el ements positions are determined by means of a simple formula and the elements completely fill the containing mother volume G4PVParameterised a physical volume representing many touch able detector elements differing in their positioning and dimensions Both are calculated by means of a G4VParameterisation object Each element s position is calculated as per G4PVReplica and each ele ment s shape can be modified by means of a user supplied formula G4VPVParameterisation a parameterisation class able to com pute the transformation and indirectly the dimensions of parame terised volumes given a replication number G4SmartVoxelProxy a class for proxying smart voxels The class represents either a header in turn refering to more VoxelProxies or a 3l node Tf created as a node calls to GetHeader cause an exception and likewise GetNode when a header G4Smart VoxelHeader represents a single axis of virtual division Contains the individual divisions which are potentially further divided along different axes G4Smart VoxelNode a single virtual division containing the phys ical volumes inside its boundaries and those of its parents G4VoxelLimits represents limitation restrictions of space where restrictions are
35. Geant4 User s Guide For Toolkit Developers June 28 2005 Contents I Introduction 1 Introduction 1 1 Scope of this manual 2 ee uo GP eee K K K K K K K 1 2 How to use this manual A K K K K K K K K K 1 3 User Requirements Document 1 4 Status of thischapter 2 II Design and Function of Geant4 Categories 2 Introduction 3 Run 3 1 Design Philosophy 2 02 4 20 64 4 2 48 oe KI K K BS Y s 52 Class De iB k duet A ete doe obs xd 3 3 Status of this chapter ase Gover ae ote K K Bl RAS ETE PS 4 Event 4 1 Design Philosophy 2 2 Class DDOSIBTIS lt ot cs Ji d n etg Sce xa ka wa ran da appeet E Your 3 4 3 Status of this chapter eu vase asa ae asta ee EIE RU 5 Tracking 5 1 Design Philosophy 2 23 2 25 240 6 888 d 5 2 Class Design soe Row ee boxe SRO eS SS ee s 5 3 Tracking Algorithm 3 2c ech ep pes K K K K K K K K K KK 5 4 Interaction with Physics Processes 5 5 Ordering of Methods of Physics Processes 5 6 Status of this chapter 2 ox ae K K KI K K K K 6 Physics Processes 6 1 Design Philosophy 6 2 Clase Desig A dero 4 danl na zU Wl alan te X tan ded eus 62 1 General 4 use o uos oet kl n i n k n cafu i m d 6 3 Status of this chapter aoaaa aaa K KEK K K 7 Hits and Digitization 7 1 Design Philosophy ars s e
36. GetHeader GetNode 1 IsHeader G4SmartVoxelNode 0 acc eii fcontents G4SliceVe fNodd a 1 Ki GetMaxEquivalentSlice d GetMinEquivalentSlice GetNoContained Fi Get Volume Sinsert 7 1 fcontents ri 1 V 1 iy G4SliceVector G4ProxyVector fslices x zi S P f 7 Wn U j GAVoxelLimits G4int E ebe N from globa l Ao r addLimit SORENE clipToLimits vector GetMaxExtent eee from STL std GetMinExtent SInside amp outCode Figure 20 12 Smart Voxels 96 G4DrawVoxels 7 createPlacedPolyhedra prawVoxels SSetVoxelsVisAttributes Figure 20 13 Navigator 97 Figure 20 14 Regions 98
37. HitsCollecti 7 qu hambertitscoi T pe RUE ioe amp H i G4Allocator from Globals Quee ER RR a A D s counterHits CollScia i counter lt counterHit o rad nArray rd eman a SS OM d idi Figure 7 2 User hit classes P ud Se G4VSensitiveDe tector 2 Wes _ GA4VReadOutG eometry build includeList lt dno ee MCN y 3 N G4GRSVolume G4Sensitive ol N from Geometry umeList N0 n ES p checkLV deer se peel E j checkPV __ G4GRSSolid M d PA G4VPhysical o from Geometry ka lt Volume fron on Figure 7 3 Readout geometry 21 G4VTouchable gt from Geometry i here 7 3 Status of this chapter 27 06 05 section on design philosophy added from Geant4 general paper by D H Wright 28 Chapter 8 Geometry 8 1 Design Philosopy The geometry category provides the ability to describe a geometrical struc ture and propagate particles efficiently through it This is done in part with the aid of two central concepts the logical and physical volumes A logical volume represents a detector element of a given shape which may contain other volumes and which may have other attributes It has access to other information which is independent of its phyisical location in the detector such as material and sensitive detector behavior A physical volume repre sents the spatial pos
38. Look at the code and use it to build your graphics system You might also find it useful to look at ASCIITree and VTree as an example of a minimal graphics system Look at FukuiRenderer as an example of a system which implements AddSolid methods for some solids Look at OpenGL as an example of a system which implements a graphical database display lists and the machinery to decide when to rebuild OpenGL is complicated by the proliferation of combinations of the use or not of display lists for three window systems X windows X with motif interactive Microsoft Windows Win32 a total of six combina tions and much use is made of inheritance to avoid code duplication 6 If it requires external libraries introduce two new environment vari ables G4VIS_BUILD_XXX_DRIVER and G4VIS_USE_XXX where XXX is your choice as above and make the modifications to e source visualization management include G4VisExecutive icc e source visualization management src G4VisManager cc e config G4VIS_BUILD gmk e config G4VIS_USE gmk 13 3 Modeling sub category e G4VModel a base class for visualization models A model is a graphics system indepedent description of a Geant4 component The sub category visualization modeling defines how to model a 3D scene for visualization The term 3D scene indicates a set of visualizable compo nent objects put in a 3D world A concrete class inheriting from the abstract base class G4V Model defines a model
39. ParticleChange Update G4Track according to ParticleChange after each PostStep Dolt Update safety after each invocation of PostStepDolts The secondaries from ParticleChange are stored to SecondaryList Then for each secondary It is checked if its kinetic energy is smaller than the energy threshold for the material In this case the particle is as signed a 0 kinetic energy and its energy is added as de posited energy of the parent track This check is only done if the flag ApplyCutFlag is set for the particle by default it is set to false for all particles user may change it in its G4VUserPhysicsList If the track has the flag IsGoodFor Tracking true this check will have no effect used mainly to track particles below threshold The parentID and the process pointer which created this track are set The secondary track is added to the list of secondaries If it has 0 kinetic energy it is only added if it it invokes a rest process at the beginning of the tracking The track status is set according to what the process defined The method G4SteppingManager InvokeAtRestDolts is called instead of the three above methods in case the track status is fStopAndALive It is on charge of selecting the rest process which has the shortest time before and then invoke it e To select the process with shortest tiem the AtRestGPIL method of all active processes is called Each process returns an lifetime and the min
40. SE y 7L8 n 19 AlongStepDolt s j GAs SS AlongStepGetPhysicalinteractionLength fom Track 2 AtRestDolt Ka KNN Posiion G4ThreeVecioI V AtRestGetPhysicalinteractionLength Heve 7 Time G4double BuildPhysicsTable _G4Material 1 woth GetPhysicsTable ba Sy from Materials NET Ts GetProcessName 1 E 1 uns PostStepDolt fDynamicParticle 3 137 3 p PostStepGetPhysicallnteractionLength ji j G4DynamicParticle G4Stp Y das from ParticleDefinition from Track P d t GetMomentumDirection S fpPreStepPoint GetTotalEnergy fPostStepPoint Figure 6 1 Management of Physics Processes 23 G4VRestContinouousDiscrete Process M Fi pave counueds N AtRestDolt P anan pU Pe ___Process p AlongStepDolt s T Gele MU Tin L G4VProcess N GelContinuousStepLimi n NS PostStepDolt AlongStepDolt x x AtRestDolt 4 N AlongStepDolt AlongStepGetPhysicallnteractionLength G iMeanLifeTime e GetContinuousStepLimit A AtRestDolt i be x d S S R AtRestGetPhysicallnteractionLength PostStepDolt L tPhysicallnteractionLength Y 2 Fi PostStepGe GAVContinousDiscrete G4VRestProcess j Process GetMeanLifeTime P N rn AtRestDolt e RRA j S pon SY i AlogStepDo PE ie r 3 A GetMeanFreePath N AT Po
41. We expect pField to point to pField 9 This amp the order of the components of pField is your own convention We calculate the value of pField at Point A new Equation of Motion for the new Field Once you have created a new type of field you must create an Equation of Motion for this Field This is required in order to obtain the force that a particle feels To do this you must inherit from G4Mag_EqRhs and create your own equation of motion that understands your field In it you must implement the virtual function EvaluateRhsGivenB Given the value of the field this function calculates the value of the generalised force This is the only function that a subclass must define virtual void EvaluateRhsGivenB const G4double yl const G4double B 3 G4double dydx const 0 In particular the derivative vector dydx is a vector with six components The first three are the derivative of the position with respect to the curve length Thus they should set equal to the normalised velocity which is components 3 4 and 5 of y 62 dydx 0 dydx 1 dydx 2 y 3 y 4 y 5 The next three components are the derivatives of the velocity vector with respect to the path length So you should write the force components for dydx 3 dydx 4 and dydx 5 for your field Get a G4FieldManager to use your field In order to inform the GEANT4 system that you want it to use your field as the global field you must do th
42. are necessary in this category The material category implements the facilities necessary to describe the physical properties of materials for the simulation of particle matter interac tions Characteristics like radiation and interaction length excitation energy loss coefficients in the Bethe Bloch formula shell correction factors etc are computed from the element and if necessary the isotope composition The material category also implements facilities to describe surface prop erties used in the tracking of optical photons 11 2 Class Design The object oriented design of the materials related classes is shown in the class diagram Fig 11 1 The diagram is described in the Booch notation 11 3 Status of this chapter 27 06 05 section on design philosophy add from Geant4 general paper by D H Wright 40 tea pA RWTPIrOr 7 Figure 11 1 Materials deredVect gro RWTools d 2 oo UNS 4 ps 558 we TS z M P zT lt wi Ana PE Galsotope gt G4Material p G4Element PEE Table C Ge f 7m T E uw Pez EN 2 1 SNL 1 P TU 1 1 theMaterialTable i theElementTable thelsotop n END I 1 n v 1 n MEE G4Material N ay bec od NAA 2 AGE j z G4Element gt G lsotope omen Addlso
43. ares a minimal interface of only one pure virtual method G4VParticleChange ApplyYourself const G4Track amp G4Nucleus amp G4HadronicProcess provides a registry for final state production models in heriting from G4HadronicInteraction Again final state production model is meant in very general terms This can be an implementation of a quark gluon string model a sampling code for ENDF B data formats 5 or a parametrisation describing only neutron elastic scattering off Silicon up to 300 MeV 72 Isotope production For isotope production a base class G4VIsotope Production is provided It declares a method G4IsoResult GetIsotope const G4Track amp const G4Nucleus amp that calculates and returns the isotope production information Any con crete isotope production model will inherit from this class and implement the method Again the modeling possibilities are not limited and the im plementation of concrete production models is not restricted in any way By convention the GetIsotope method returns NULL if the model is not applicable for the current projectile target combination Framework functionality Cross Sections G4HadronicProcess provides registering possibilities for data sets A default is provided covering all possible conditions to some approximation The process stores and retrieves the data sets through a data store that acts like a FILO stack a Chain of Responsibility with a First In Last Out decision st
44. ated classes is shown in the class diagram Fig 14 1 The diagram is described in the Booch nota tion E V S EP Pt VOTER Z 3 tts CN G4VisManager D G4Ulmanager visManager addNewCommand e 3 f applyCommand getCurrentDoubleValue j getCurrentintValue e TAW getCurrentStringValue UlManag r j d i getCurrentVdlues Noe Eus Che einen i fT T N inter F Jj fUlmanager G4UImanager J BAU G4Ulicl gt SJi e T an C den FM EXIT and other S j J Bira 1 wot control m l nz 4 i z commands M7 GUIS Pd a7 A e N session e G4Ulcontrol Fi i Messenger PES MILES i J en hd ee G4Ulsession N w 7 jetCommand 4 9 promi 0 7 e kaza a C sessionStart 7d Ra ___ sessionTerminate G UlcommandTree r WW gt adaNewCommand J findPath p ra li nist A W G4Ulmessenger N listCurren 4 uc j S tree G4UlcommandTree Se varie 7 Pa dictan N 3 addUlcommand These two classes are shown just for illustrating how classes in other ji Pene Andr Pp categories use the messenger G4Ulbatch Pe c accen ees Sdr messengerA should know all of 4 GAUlterminal gt i vA 2 nessesary set get methods of C Em d Seah
45. bed in the Booch notation Fig 10 1 shows a general overview of the particle classes Fig 10 2 shows classes related to the particle table Fig 10 3 shows the classes related to the particle decay table 37 GaGeantino 4MuonPlus gt GaMwonMinus G4PionPlus G4Proton Geantino lt Me A md GetCuts 7 GetCuts A Geicuts GetCuts 7M Setus a SE MuonMinus y o PionPlus V Cols TET Br and many others w SetCutet UNE SetCuts v SetCuts Proton i p QU Qo Hk mr c Mn 1 T X funt e Gal G4VBoson n G4VLepton lt G4VMeson G4VBaryon 7 r r Nat ae L N wW n E RGE G4LossVectc r B PEN w ra G4LossTable e La CN AA insert _G4Material G4ParticleWithCuts awaz rr from Materials A SetCuts _theLosstable i LAT ea Se 0 n ncc LEE a BuildPhysicsTable M cs 091 x CalcEnergyCuts Sod M cm T Pa Na ComputeLoss G4RangeVector EOS E GetEnergyCuts y etValue r GALossVector rep eat N a MELLE PutValue i y GetValue pH G4Allocator IN n N S PutValue 1 from Globals il Ure Th G ParticleDefinition Woo Do lt j thePDGMass G4double Pi G4Process gt 3 2 theParticleName G4String 1 A d G4DynamicParticle t thePDGEncoding G
46. bility to add user defined data sets in a seamless manner 4 Flexible unconstrained choice of final state production models 5 Ability to use different final state production codes for different parts of the simulation depending on the conditions at the point of interaction 6 Ability to add user defined final state production models in a seamless Manner 7 Flexible choice of isotope production models to run in parasitic mode to any kind of transport models 69 8 Ability to use different isotope production codes for different parts of the simulation depending on the conditions at the point of interaction 9 Ability to add user defined isotope production models in a seamless manner Design and interfaces The above requirements are implemented in three framework components one for cross sections final state production and isotope production each The class diagrams are shown in figure 18 2 for the cross section aspects figure 18 3 for the final state production aspects and figure 18 4 for the isotope production aspects Abstract G4HadronicP rocess W vlrtunt gt gt Gethiicrosc opie Cros sSactioni b vrtunt gt gt PostStepDob Aragan amp ChoossHadr one inier ach oni WG aneratPoatStepDo lb W lt lt tatlc gt gt Get otopsFrocuctien infor tReg sterk otopaPr cduchonf 1odsl stati Enab kotopsProdudi onl obat yi static Di qabi sis otopsFr ode bon lobally Enable kotops Cicourti rg Ol sabls kcte
47. cal providing specific code for optical photons e utils collecting utility classes used by the above packages It provides the features of openness and extensibilty resulting from the use of object oriented technology alternative physics models obeying the same process abstract interface are often available for a given type of interaction 21 For hadronic physics an additional set of implementation frameworks was added to accommodate the large number of possible modeling approaches The top level framework provides the basic interface to other GEANT4 cate gories It satisfies the most general use case for hadronic shower simulations namely to provide inclusive cross sections and final state generation The frameworks are then refined for increasingly specific use cases building a hi erarchy in which each level implements the interface specified by the level above it A given hadronic process may be implemented at any one of these levels For example the process may be implemented by one of several mod els and each of the models may in turn be implemented by several sub models at the lower framework levels 6 2 Class Design 6 2 1 General The object oriented design of the generic physics process G4VProcess and its relation to the process manager is shown in Fig 6 1 Fig 6 2 shows how specific physics processes are related to G4VProcess 6 3 Status of this chapter 27 06 05 section on design philosophy added by D H Wright
48. ce in the code of the surface So special care must be taken to handle these cases in considering all different possible scenarios in order to respect the specifications and allow the solid to be used correctly by the other components of the geometry module Creating a derived class of G4VSolid The solid must inherit from G4VSolid or one of its derived classes and implement its virtual functions Mandatory member functions you must define are the following pure vir tual of G4VSolid EInside Inside const G4ThreeVector amp p G4double DistanceToIn const G4ThreeVector amp p G4double DistanceToIn const G4ThreeVector amp p const G4ThreeVector amp v G4ThreeVector SurfaceNormal const G4ThreeVector amp p G4double DistanceToOut const G4ThreeVector amp p G4double DistanceToOut const G4ThreeVector amp p const G4ThreeVector amp v const G4bool calcNorm false G4bool validNorm 0 G4ThreeVector n G4bool CalculateExtent const EAxis pAxis const G4VoxelLimits amp pVoxelLimit const G4AffineTransform amp pTransform G4double amp pMin G4double amp pMax const G4GeometryType GetEntityType const Std ostream amp StreamInfo std ostream amp os const They must perform the following functions EInside Inside const G4ThreeVector amp p This method must return e kOutside if the point at offset p is outside the shape boundaries plus Tolerance 2 e kSurface if the point is lt Tolerance 2 from a surface or e kInside other
49. ck given by a physics process This is done through the UpdateStepForAlongStep method of the ParticleChange Then for each secondary It is checked if its kinetic energy is smaller than the energy threshold for the material In this case the particle is as signed a 0 kinetic energy and its energy is added as de posited energy of the parent track This check is only done if the flag ApplyCutFlag is set for the particle by default it is set to false for all particles user may change it in its G4VUserPhysicsList If the track has the flag IsGoodFor Tracking true this check will have no effect used mainly to track particles below threshold The parentID and the process pointer which created this track are set The secondary track is added to the list of secondaries If it has 0 kinetic energy it is only added if it it invokes a rest process at the beginning of the tracking The track status is set according to what the process defined The method G4SteppingManager InvokePostStepDolts is on charge of calling the PostStepDolt methods of the different processes e Invoke the PostStepDoIt methods of the specified discrete process the one selected by the PostStepGetPhysicalInteractionLength and they return the ParticleChange The order of invocation of processes is inverse to the order used for the GPIL methods After it for each process the following is executed 16 Update PostStepPoint of Step according to
50. clhep manual RefGuide index html or the CLHEP User Manual http cern ch wwwasd lhc 4 clhep manual UserGuide index html 46 Pena DE WENN a ngines PN AN nan e gt 3 due e ue Y PoissonDi gt 3 flat ret RD stribution Ne a NS J pP E _ _ FlatDistrib yp hest BWDistrib uton N ution N PE GaussDist E s utlo C ribution M e o eu z N Pad aa Figure 12 4 Shooting with arbitrary engines 12 3 Status of this chapter 01 12 02 minor update by G Cosmo 18 06 05 introductory paragraphs added and minor grammar changes by D H Wright AT Chapter 13 Visualization 13 1 Design Philosophy The visualization category consists of the classes required to display detector geometry particle trajectories tracking steps and hits It also provides visualization drivers which are interfaces to external graphics systems A wide variety of user requirements went into the design of the visualiza tion category for example e very quick response in surveying successive events e high quality output for presentation and documentation e flexible camera control for debugging detector geometry and physics e selection of visualizable objects e interactive picking of graphical objects for attribute editing or feedback to the associated data e highlighting incorrect intersections of physical volumes e co working with graphical use
51. d An example of the use of this functionality is the study of activation of a Germanium detector in a high precision low background experiment 18 5 Level 3 Framework Theoretical Models on xt rr G 4Hadroricirt eractior congas Gt Theo FSGenerator G4Parten TranspoitModal oan bi at cac qx ruw mm prat 64 VHighEnerayGenerator omm ES j aca ero i s Ava DUIONON LEUR mrm mra aaraa X GaVIntraNuclearTr an sport lod el G4NhModel ER cona vw Wan kan cxi Qeropanaten G4V Excitabon Handler b ya ounaia uem s G4V Parton Sringhlodal T Pa j Wak amo S et IDUPIONOE LE UR d Xwera rng m RE gt come E congas G4 PythiaNh rteriace pL LN G4 HadronKineticModel cue G4HadronicCaecade Figure 18 5 Level 3 implementation framework of the hadronic category of GEANTA theoretical model aspect 74 GEANTA provides at present one implementation framework for theory driven models The main use case is that of a user wishing to use theo retical models in general and to use various intra nuclear transport or pre compound models together with models simulating the initial interactions at very high energies Requirements 1 Allow to use or adapt any string parton or parton transport 8 model 2 Allow to adapt event generators ex PY THIA 9 for final state pro duction in shower simulation 3 Allow for combination of the above with any intra nuclear transport INT 4 Allow stand alone use
52. defined e false if the solid does not lie entirely behind or on the exiting surface If calcNorm is false then validNorm and n are unused G4bool CalculateExtent const EAxis pAxis const G4VoxelLimits amp pVoxelLimit const G4AffineTransform amp pTransform G4double amp pMin G4double amp pMax const 57 Calculate the minimum and maximum extent of the solid when under the specified transform and within the specified limits If the solid is not inter sected by the region return false else return true G4GeometryType GetEntityType const Provide identification of the class of an object required for persistency and STEP interface std ostream amp StreamInfo std ostream amp os const Should dump the contents of the solid to an output stream The method G4double GetCubicVolume should be implemented for every solid in order to cache the computed value and therefore reuse it for future calls to the method and to eventually implement a precise computation of the solid s volume If the method will not be overloaded the default implementation from the base class will be used estimation through a Monte Carlo algorithm and the computed value will not be stored There are a few member functions to be defined for the purpose of visu alisation The first method is mandatory and the next four are not Mandatory virtual void DescribeYourselfTo G4VGraphicsScene amp scene const 0 Not mandatory
53. e following steps 1 Create a Stepper of your choice yourStepper new G4ClassicalRK yourEquation fMotion or if your field is not s nooth eg new G4ImplicitEuler yourEquation0fMotion 2 Create a chord finder that uses your Field and Stepper You must also give it a minimum step size below which it does not make sense to attempt to integrate yourChordFinder new G4ChordFinder yourField yourMininumStep say 0 01 mm yourStepper 3 Next create a G4FieldManager and give it that chord finder yourFieldManager new G4FieldManager yourFieldManager SetChordFinder yourChordFinder 4 Finally we tell the Geometry that this FieldManager is responsible for creating a field for the detector G4TransportationManager GetTransportationManager gt SetFieldManager yourFieldManager 63 Changes for non electromagnetic fields If the field you are interested in simulating is not electromagnetic another minor modification may be required The transportation currently chooses whether to propagate a par ticle in a field or rectilinearly based on whether the particle is charged or not If your field affects non charged particles you must inherit from the G4Transportation and re implement the part of GetAlongStepPhysicalInter actionLength that decides whether the particles is affected by your force In particular the relevant section of code does the following Does the particle have an EM field force exerti
54. en be informed of the new field A new Field class A new type of Field class may be created by inheriting from G4Field class NewField public G4Field 1 public void GetFieldValue const double Point 3 double pField 0 T and deciding how many components your field will have and what each com ponent represents For example three components are required to describe a vector field while only one component is required to describe a scalar field If you want your field to be a combination of different fields you must choose your convention for which field goes first which second etc For example to define an electromagnetic field we follow the convention that components 0 1 and 2 refer to the magnetic field and components 3 4 and 5 refer to the electric field 61 By leaving the GetFieldValue method pure virtual you force those users who want to describe their field to create a class that implements it for their detector s instance of this field So documenting what each component means is required to give them the necessary information For example someone can describe DetectorAbc s field by creating a class DetectorAbcField that derives from your NewField class DetectorAbcField public NewField 1 public void MyFieldGradient GetFieldValue const double Point 3 double pField They then implement the function GetFieldValue void MyFieldGradient GetFieldValue const double Point 3 double pField
55. eractions of a track or tracks in a sensitive detector component A digitization or digit represents a detector output such as an ADC TDC count or a trigger signal A digit is created from one or more hits and or other digits Given the wide variety of GEANT4 applications ways of describing detector sensitivity and the quantities to be stored in the hits and digits vary greatly This category therefore provides only abstract classes for both detector sensitivity and hits digits It also provides tools for organizing the hits digits into collections 7 2 Class Design G4SensitiveDetector Manager a list of G4SensitiveDetectors G4HitsStructure a tree like structure of G4Hit collections Each branch represents the hits in given sub detector For example the first level of branches may consist of a tracker ECAL and HCAL while the second level in HCAL consists of the barrel and endcaps Finally the barrel may have phi slices Z slices etc G4VSensitiveDetector an abstract class of all of sensitive volumes G4HitsCollection a collection of hits Instantiates an RWCollection class G4VHit this class has all the information about a particular hit caused by a single step 25 G4SDManager activate addNewDetector y get collectionCapacity get collectionID d 4 prepareNewEvent WyterminateCurrentEvent me v5 G4NICmessen G4SDmessenger gy manager ger a from
56. ess pointer which created this track are set The secondary track is added to the list of secondaries If it has 0 kinetic energy it is only added if it it invokes a rest process at the beginning of the tracking The track is updated and its status is set according to what the process defined 5 5 Ordering of Methods of Physics Processes The ProcessManager of a particle is responsible for providing the correct ordering of process invocations G4SteppingManager invokes the processes at each phase just following the order given by the ProcessManager of the corresponding particle For some processes the order is important GEANT4 provides by default the right ordering It is always possible for the user to choose the order of process invocations at the initial set up phase of GEANT4 This default ordering is the following 1 Ordering of GetPhysicalInteractionLength e In the loop of GetPhysicalInteractionLength of AlongStepDolt the Transportation process has to be invoked at the end 18 e In the loop of GetPhysicalInteractionLength of AlongStepDolt the Multiple Scattering process has to be invoked just before the Transportation process 2 Ordering of Dolts e There is only some special cases For example the Cherenkov process needs the energy loss information of the current step for its Dolt invocation Therefore the EnergyLoss process has to be invoked before the Cherenkov process This ordering is provided by the process
57. f Command rolls back to G4TheoFSGenerator accumulating the information produced in the various levels of delegation 18 6 Level 4 Frameworks String Parton Mod els and Intra Nuclear Cascade lt Abstract gt G4 VPartonStringModel Seeattero lt lt Push Abstract gt gt 0 G4 VSming Fragmertabon lt E MM Gt Excited Sting Fragmertsatra amp lt lt vrtuabt gt gt GstSirings0 yy Cor sctHacr nt Aomenta feste Ponta lt lt Concietes gt z G4PythaFragmentatonintertace Dealt FARE e ire A j GAFT F oda WGatsirirga0 Con etes DGuk WG ah y oUndsdhlud sus GiLongtudnalStingDecay anne f D afeidtsParticipants j APET cate Sota ng yEukiSnnga i Tro Gaus qari af Chooss X 0 Figure 18 6 Level 4 implementation framework of the hadronic category of GEANTA parton string aspect The use cases of this level are related to commonalities and detailed choices in string parton models and cascade models They are use cases of an expert user wishing to alter details of a model or a theoretical physicist wishing to study details of a particular model Requirements 77 lt lt P rsly Abstracts GA4Vn1raNudearTrarspa1ocdel WApp jYourself G4VKinalicNUclaon SPropagats scan eens a S Getdlvkmentum We stDsf nihon GetiPasihon G4VaDIwdeus x Sinn I Concrete Pae E gt lt lt gt gt Gtia Plumber G4Hadron KinetciAadel Adv UA een 3 j AST
58. h the GAVExcitationHandler interface and provides concrete implementations with the possibility of delegating the decay of a compound nucleus The concrete scenario of G4TheoFSGenerator using a dual parton model and a classical cascade which in turn uses an exciton pre compound model that delegates to an evaporation phase would be the following G4TheoFS Generator receives the conditions of the interaction a primary particle and a nucleus It asks the dual parton model to perform the initial scatterings and return the final state along with the by then damaged nucleus The nu cleus records all information on the damage sustained G4TheoFSGenerator forwards all information to the classical cascade that propagates the parti 16 cles in the already damaged nucleus keeping track of interactions further damage to the nucleus etc Once the cascade assumptions break down the cascade will collect the information of the current state of the hadronic system like excitation energy and number of excited particles and interpret it as a pre compound system It delegates the decay of this to the exciton model The exciton model will take the information provided and calculate transitions and emissions until the number of excitons in the system equals the mean number of excitons expected in equilibrium for the current excita tion energy Then it hands over to the evaporation phase The evaporation phase decays the residual nucleus and the Chain o
59. imum one is chosen This method returm also a G4ForceCondition flag to indicate if the process is forced or not Forced Correspond ing AtRestDolt is forced NotForced Corresponding AtRestDolt is not forced unless this process limits the step e Set the step length of current track and step to 0 e Invoke the AtRestDoIt methods of the specified at rest process and they return the ParticleChange The order of invocation of processes is inverse to the order used for the GPIL methods 17 After it for each process the following is executed Set the current process as a process which defined this Step length Update the G4Step information by using final state information of the track given by a physics process This is done through the UpdateStepForAtRest method of the ParticleChange The secondaries from ParticleChange are stored to SecondaryList Then for each secondary It is checked if its kinetic energy is smaller than the energy threshold for the material In this case the particle is as signed a 0 kinetic energy and its energy is added as de posited energy of the parent track This check is only done if the flag ApplyCutFlag is set for the particle by default it is set to false for all particles user may change it in its G4VUserPhysicsList If the track has the flag IsGoodFor Tracking true this check will have no effect used mainly to track particles below threshold The parentID and the proc
60. it Functionality explains in some detail how to extend the functionality of Geant4 Most of the class categories are covered and some which are especially useful to most users are covered in greater detail It is not necessary to understand the entire manual before adding a new functionality To add a new physics process for example only the following items must be read and understood e the design principle described in the Physics processes section of Chapter 2 e techniques explained in the Physics processes section of Chapter 3 1 3 User Requirements Document At the beginning of Geant4 development a set of user requirements was collected in order to inform the object oriented analysis and design of the toolkit The User Requirements Document follows the PSS 05 software en gineering standards and is available at http cern ch geant4 00AandD URD pdf This document provides a general description of the main capabilities and constraints of the toolkit It also defines three types of users characterized by their level of interaction with the system Specific requirements are also listed and classified 1 4 Status of this chapter 24 06 05 re organized and re written by D H Wright Part II Design and Function of Geant4 Categories Chapter 2 Introduction Geant4 exploits advanced software engineering techniques based on the Booch UML Object Oriented Methodology and follows the evolution of the ESA Softwa
61. itioning or placement of the logical volume with respect to an enclosing mother logical volume Thus a hierarchical tree structure of volumes can be built with each volume containing smaller volumes which may not overlap Repetitive structures can be represented by specialized physical volumes such as replicas and parameterized placements sometimes resulting in a large savings in memory In GEANT4 the logical volume has been refined by defining the shape as a separate entity called a solid Solids with simple shapes like rectilinear boxes trapezoids spherical or cylindrical sections or shells each have their properties coded separately in accord with the concept of Constructed Solid Geometry CSG More complex solids are defined by their bounding surfaces which can be planes second order surfaces or higher order B spline surfaces and belong to the Boundary Representations BREP sub category Another way to build solids is by boolean combination union intersec tion and subtraction The elemental solids should be CSGs Although a detector is naturally and best described as by a hierarchy of volumes efficiency is not critically dependent on this An optimization technique called voxelization allows efficient navigation even in flat ge 29 ometries typical of those produced by CAD systems 8 2 Class Design e G4GeometryManager responsible for managing high level ob jects in the geometry subdomain notably inc
62. ke InvokeAtRestDolItProcs for the selected AtRest processes 3 If particle is not stopped e Invoke DefinePhysicalStepLength that finds the minimum step length demanded by the active processes 14 5 4 e Invoke InvokeAlongStepDoltProcs e Update current track properties by taking into account all changes by AlongStepDolt e Update the safety e Invoke PostStepDolt of the active discrete process e Update the track length e Send G4Step information to Hit Dig if the volume is sensitive e Invoke the user intervention process e Return the value of the StepStatus Interaction with Physics Processes The interaction of the tracking category with the physics processes is done in two ways First each process can limit the step length through one of its three GetPhysicalInteractionLength methods AtRest AlongStep or PostStep Second for the selected processes the DoIt AtRest AlongStep or PostStep methods are invoked All this interaction is managed by the Stepping method of G4SteppingManager To calculate the step length the DefinePhysicalStepLength method is called The flow of this method is the following Obtain maximum allowed Step in the volume define by the user through G4UserLimits The PostStepGetPhysicalInteractionLength of all active processes is called Each process returns a step length and the minimum one is chosen This method also returns a G4ForceCondition flag to indicate if the process is forced or n
63. low energy neutron transport with a quantum molec ular dynamics 6 or chiral invariant phase space decay 7 model in the case of tracker materials and fast parametrised models for calorimeter materials 73 with user defined modeling of interactions of spallation nucleons with the most abundant tracker and calorimeter materials Isotope production The G4HadronicProcess by default calculates the isotope production information from the final state given by the transport model In addition it provides a registering mechanism for isotope pro duction models that run in parasitic mode to the transport models and inherit from G4VIsotopeProduction The registering mechanism behaves like a FILO stack again based on Chain of Responsibility The models will be asked for isotope production information in inverse order of registration The first model that returns a non NULL value will be applied In addition the G4HadronicProcess provides the basic infrastructure for accessing and steering of isotope production information It allows to enable and disable the calculation of isotope production information globally or for individual processes and to retrieve the isotope production information through the G4IsoParticleChange GetIsotopeProductionInfo method at the end of each step The G4HadronicProcess is a finite state machine that will ensure the Get IsotopeProductionInfo returns a non zero value only at the first call after isotope production occurre
64. luding opening and closing locking the geometry and creating deleting optimization informa tion for G4Navigator The class is a singleton e G4LogicalVolumeStore a container for optionally storing created logical volumes It enables traversal of all logical volumes by the UI user etc e G4LogicalVolume represents a leaf node or unpositioned subtree in the geometry hierarchy It may have daughters ascribed to it and is also responsible for retrieval of the physical and tracking attributes of the physical volume that it represents These attributes include solid material magnetic field and optionally user limits sensitive detectors etc Logical volumes are optionally entered into the G4LogicalVolumeStore e G4MagneticField a class responsible for the magnetic field in each volume including the calculation of particle trajectories along curved paths In cases where the geometry step limits the particle s step the distance calculated is guaranteed to be the distance to a volume boundary e G4Navigator a class used by the tracking management able to ob tain calculate tracking time geometrical information such as distance to the next volume or to find the physical volume containing a given point in the world reference system The navigator maintains a trans formation history and other information used to optimize the tracking time performance e G4NavigationHistory responsible for maintenance of the history of
65. meworks for hadronic generators in GEANTA and illustrate the physics models underlying hadronic shower simulation on examples including the three basic types of modeling data driven parametrisation driven and theory driven modeling and their possible realisations in the Object Oriented component system of GEANT4 We put particular focus on the level of extendibility that can and has been achieved by our Russian dolls approach to Object Oriented design and the role and importance of the frameworks in a component system 18 2 Principal Considerations The purpose of this section is to explain the implementation frameworks used in and provided by GEANTA for hadronic shower simulation as in the 1 1 re lease of the program The implementation frameworks follow the Russian dolls approach to implementation framework design A top level very ab stracting implementation framework provides the basic interface to the other GEANTA categories and fulfils the most general use case for hadronic shower simulation It is refined for more specific use cases by implementing a hier archy of implementation frameworks each level implementing the common logic of a particular use case package in a concrete implementation of the 66 interface specification of one framework level above this way refining the granularity of abstraction and delegation This defines the Russian dolls ar chitectural pattern Abstract classes are used as the delegation mechanism
66. n arbitrary graphics system can easily be plugged in to GEANT4 The plugged in graphics system is then available for visualizing detector simulations The set of three concrete classes mentioned in the last item is called a visualization driver The DAWN File driver for example is the interface to the Fukui Renderer DAWN and is implemented by the following set of classes 1 GAaDAWNFILE public G4VGraphicsSystem for initialization 2 GADAWNFILESceneHandler public G4VSceneHandler for modeling 3D scenes 3 GADAWNFILEView public G4V View for rendering 3D scenes Several visualization drivers are already prepared by default They are com plementary to each other in many aspects For details see Chapter 8 of the User s Guide for Application Developers To create a new graphics system for GEANTA it is necessary to implement a new set of three classes composing a new visualization driver A skeleton set of classes is included in the visualization category under subdirectory visualization XXX but not normally registered recommended approach is to copy the contents of XXX to a new subdirectory with a name that suits your new system Then 49 1 Change the name of the files change XXX to something that suits your system 2 Change XXX similarly in all files 3 Change XXX similarly in name G4XXX in GNUmakefile 4 Add your new subdirectory to SUBDIRS and SUBLIBS in visualiza tion GNUmakefile 5
67. nce the start of step ping the identification of the geometrical volume which contains the particle etc Dynamic information such as particle momentum and en ergy is held in the class through a pointer to the G4DynamicParticle class Static information such as the particle mass and charge is stored in the G4DynamicParticle class through the pointer to the G4ParticleDefinition class Here the aggregation hierarchical de sign is extensively employed to maintain high tracking performance e G4TrajectoryPoint and G4 Trajectory the class G4TrajectoryPoint holds the state of the particle after propagating one step Among other things it includes information on space time energy momentum and geometrical volumes G4Trajectory aggregates all G4TrajectoryPoint objects which belong to the particle being propagated G4TrackingManager takes care of adding the G4TrajectoryPoint to a G4Trajectory object if the user requested it see 1 The life of a G4Trajectory object spans an event contrary to G4Track objects which are deleted from memory after being processed e G4UserTrackingAction and G4UserSteppingAction G4UserTrackingAction is a base class from which user actions at the beginning or end of track ing may be derived Similarly GAUserSteppingAction is a base class from which user actions at the beginning or end of each step may be derived 5 3 Tracking Algorithm The key classes for tracking in GEANT4 are G4TrackingManager and G4Step
68. ng upon it if particleCharge 0 0 fieldExertsForce this gt DoesGlobalFieldExist Future will can also check whether current volume s field is Zero or set by the user in the logical volume to be zero J and you want it to ask whether it feels your force If for the sake of an example you wanted to see the effects of gravity on a heavy hypothetical particle you could say Does the particle have my field s force exerted on it if particle gt GetName VeryHeavyWIMP fieldExertsForce this gt DoesGlobalFieldExist For gravity J After doing all these steps you will be able to see the effects of your force on a particle s motion 16 2 Status of this chapter 10 06 02 partially re written by D H Wright 14 11 02 spell check by P Arce 64 Chapter 17 Physics Processes Adding a new electromagnetic process Adding a new hadronic process 17 1 Status of this chapter 27 06 05 under construction 65 Chapter 18 Hadronic Physics 18 1 Introduction Optimal exploitation of hadronic final states played a key role in successes of all recent collider experiment in HEP and the ability to use hadronic final states will continue to be one of the decisive issues during the analysis phase of the LHC experiments Monte Carlo programs like GEANT4 1 facilitate the use of hadronic final states and have been developed for many years We give an overview of the Object Oriented fra
69. ngth allowing tracking to request the information necessary to decide on the process responsible for final state production and one to compute the final state These are pure virtual methods and have to be implemented in each individual derived class as enforced by the compiler l The same can be achieved with template specialisations with slightly improved CPU performance but at the cost of significantly more complex designs and with present com pilers significantly reduced portability 67 Purdy Abeiract G4VProcess Posi StepGet Physical Imeracton Length Posi Sipon Along SlepGet Physical nteracton Lengi AlongSiepDon A1ReS1G 1 Physical nt eracton Langih oA RestDoN cAbE tact G4VDiscrets Process PoeiStepGetPhysical hteractien Lenghi Poce15tspDoli lt Abstract gt G4HadronicProcess amp virtual GetlAcroeccpicCroesSection 1 lt virl al gt gt PostStepDoli RegsterlAs Cheose HadrcnicInteraction General Pos154epDol1 5 lt etalic gt gt Get solope Production hio Regsterbotope Production Model lt lt stalic gt gt EnablelsctopeProductonGlobally 3 static Disable botope ProductonGloballyy Enabie EotopeC auntnoi SDisableEotcpeCcuninac x Abetact G4VReslProcess aj ResiGe1 Physicalimeracton Length ai Resi DON Figure 18 1 Level 1 implementation framework of the hadronic category of GEANT4 68 Framework functionality The functionality pr
70. of intra nuclear transport 5 Allow for combination of the above with any pre compound model 6 Allow stand alone use of any pre compound model 7 Allow for use of any evaporation code 8 Allow for seamless integration of user defined components for any of the above Design and interfaces To provide the above flexibility the following ab stract base classes have been implemented e G4VHighEnergyGenerator e G4VIntranuclearTransportModel e G4VPreCompoundModel e G4VExcitationHandler In addition the class GATheoFSGenerator is provided to orchestrate inter actions between these classes The class diagram is shown in Fig 18 5 G4VHighEnergyGenerator serves as base class for parton transport or parton string models and for Adapters to event generators This class de clares two methods Scatter and GetWoundedNucleus The base class for INT inherits from G4HadronicInteraction making any concrete implementation usable as a stand alone model In doing so 79 it re declares the ApplyYourself interface of G4HadronicInteraction and adds a second interface Propagate for further propagation after high energy interactions Propagate takes as arguments a three dimensional model of a wounded nucleus and a set of secondaries with energies and positions The base class for pre equilibrium decay models GAVPreCompoundModel inherits from G4HadronicInteraction again making any concrete imple mentation usable as stand alone model It adds
71. or iginal parameters PConeParameters original parameters PGonParameters G4CurveRayIntersection GetDistance SGetPoint GetRay G4CurveVector T 1astInten ection segments 1 So A x G4CompositeCurve amp Z7 Piet Get Segments aT ScetRshift SGetPasition G4CurvePoint GetCurve SGetPoint Reset Figure 20 7 BREP curves 91 G4STEPEntity G4SurfaceBoundary surfaceBounda GetBounds splitwithCylind 1 splitWithPlane r 7 A 0 1 projecteGBoundary ki Figure 20 8 BREP surfaces 92 G4ReflectionFactory instance G4ReflectionFactory amp fReflectedL VMap LogicalVolumesMap Place Replicate SetVerboseLevel lt lt const gt gt GetVerboseLevel lt lt static gt gt Instance G4ReflectedSolid amp fDirectTransform3D G4Transform3D amp PtrSolid G4VSolid ComputeDimensions SetDirectTransform3D const CalculateExtent lt lt const gt gt DistanceToln lt lt const gt gt DistanceToOut lt lt const gt gt GetDirectTransform3D const Inside const SurfaceNormal Figure 20 9 Reflections of solids 93
72. ot Forced Corresponding PostStepDolt is forced NotForced Corresponding PostStepDolt is not forced un less this process limits the step Conditionally Only when Along StepDolt limits the step corresponding PoststepDoIt is invoked ExclusivelyForced Corresponding PostStepDolt is exclusively forced All other Dolt including AlongStepDolts are ignored The AlongStepGetPhysicalInteractionLength method of all active pro cesses is called Each process returns a step length and the minimum of these and the This method also returns a fGPILSelection flag to indicate if the process is the selected one can be is forced or not CandidateForSelection this process can be the winner If its step 15 length is the smallest it will be the process defining the step the pro cess NotCandidateForSelection this process cannot be the winner Even if its step length is taken as the smallest it will not be the process defining the step The method G4SteppingManager InvokeAlongStepDoIts is in charge of calling the AlongStepDolt methods of the different processes e If the current step is defined by a ExclusivelyForced PostStepGet PhysicalInteractionLength no AlongStepDolIt method will be invoked e Else all the active continuous processes will be invoked and they return the ParticleChange After it for each process the following is executed Update the G4Step information by using final state information of the tra
73. ovided is through the use of process base class pointers in the tracking physics interface and the G4Process Manager All functionality is implemented in abstract and registration of derived process classes with the G4ProcessManager of an individual particle allows for arbitrary combination of both GEANT4 provided processes and user implemented processes This registration mechanism is a modification on a Chain of Responsibility It is outside the scope of the current paper and its description is available from 3 18 4 Level 2 Framework Cross Sections and Models At the next level of abstraction only processes that occur for particles in flight are considered For these it is easily observed that the sources of cross sections and final state production are rarely the same Also differ ent sources will come with different restrictions The principal use cases of the framework are addressing these commonalities A user might want to combine different cross sections and final state or isotope production mod els as provided by GEANT4 and a physicist might want to implement his own model for particular situation and add cross section data sets that are relevant for his particular analysis to the system in a seamless manner Requirements 1 Flexible choice of inclusive scattering cross sections 2 Ability to use different data sets for different parts of the simulation depending on the conditions at the point of interaction 3 A
74. pingManager The singleton object TrackingManager from G4TrackingManager keeps all 13 information related to a particular track and it also manages all actions nec essary to complete the tracking The tracking proceeds by pushing a particle by a step the length of which is defined by one of the active processes The TrackingManager object delegates management of each of the steps to the SteppingManager object This object keeps all information related to a particular step The public method ProcessOneTrack in G4TrackingManager is the key to managing the tracking while the public method Stepping is the key to managing one step The algorithms used in these methods are ex plained below ProcessOneTrack in G4TrackingManager 1 Actions before tracking the particle Clear secondary particle vector 2 Pre tracking user intervention process 3 Construct a trajectory if it is requested 4 Give SteppingManager the pointer to the track which will be tracked 5 Inform beginning of tracking to physics processes 6 Track the particle Step by Step while it is alive e Call Stepping method of G4SteppingManager e Append a trajectory point to the trajectory object if it is requested T Post tracking user intervention process 8 Destroy the trajectory if it was created Stepping in G4SteppingManager 1 Initialize current step 2 If particle is stopped get the minimum life time from all the at rest processes and invo
75. psCourtinan k Core ete runde PERRA Concrete G4HadronFissionProcess G4HadroninelasticProcess G4HadronElasticProcess G4HadronCaptureProcess Ji ji L Concrete i G4CrossSectionDataStore fy cdiDatasti SG sbCron sSechor T Concrete 10 AData Set cFuret Abstract gt ai G4VCrossSectionDataSet S EApplicatis wstCrons Sechoni lt lt Concrebe gt gt BDataSet Figure 18 2 Level 2 implementation framework of the hadronic category of GEANTA4 cross section aspect The three parts are integrated in the G4HadronicProcess class that serves as base class for all hadronic processes of particles in flight Cross sections Each hadronic process is derived from G4HadronicProcess which holds a list of cross section data sets The term data set is repre 70 lt lt Absiraci gt gt G4HadronicProcess lt lt vinual gt gt GetMicroscopicCrossSection 3 virlual PosiStepDoll Register Mel SiChooseHadro nic meraction SGeneralPosiStep Dolt etatics GellsolopeP roductionlnto Register Eotope Production ode I lt lt stalic gt gt EnablelsotopeP roductionGlobally lt lt slalic gt gt DisablelsotopeP rod uc1ionGloba lly EnableleoiopeCountina iDisablelsotopeCountina 4 lt lt Concrete gt gt D 1 G4EnergyRangeManager lt lt Absiracl gt gt 4 4Hadronicinteraction g G4Element Gea1Hadroniclnle radion N Se Apply
76. r interfaces Because it is very difficult to respond to all of these requirements with only one built in visualizer an abstract interface was developed which supports several complementary graphics systems Here the term graphics system means either an application running as a process independent of GEANT4 or a graphics library to be compiled with GEANT4 A concrete implementation of the interface is called a visualization driver which can use a graphics library directly communicate with an independent process via pipe or socket or simply write an intermediate file for a separate viewer 48 13 2 Class Design e G4VVisManager abstract base class for visualization managers e G4VisManager controls GEANT4 visualization This class creates and registers graphics systems scenes scene handlers and viewers and manages them It is a singleton and an abstract class requiring the user to derive from it a concrete visualization manager Roles and structure of the visualization manager are described in Chapter 8 of the User s Guide for Application Developers e G4VisExecutive concrete visualization manager that implements the virtual function RegisterGraphicsSystems e G4VGraphicsSystem G4VSceneHandler G4V View abstract interface classes for initialization of a graphics system modeling 3D scenes and rendering the modeled 3D scenes respectively By defining a set of three C classes inheriting from these virtual base classes a
77. rategy This allows the user to map out the entire parameter space by overlaying cross section data sets to optimise the overall result Examples are the cross sections for low energy neutron transport If these are registered last by the user they will be used whenever low energy neutrons are encountered In all other conditions the system falls back on the default or data sets with earlier registration dates The fact that the registration is done through abstract base classes with no side effects allows the user to implement and use his own cross sections Examples are special reaction cross sections of K nuclear interactions that might be used for c e analysis at LHC to control the systematic error Final state production The G4HadronicProcess class provides a regis tration service for classes deriving from G4HadronicInteraction and dele gates final state production to the applicable model G4HadronicInteraction provides the functionality needed to define and enforce the applicability of a particular model Models inheriting from G4HadronicInteraction can be restricted in applicability in projectile type and energy and can be ac tivated deactivated for individual materials and elements This allows a user to use final state production models in arbitrary combinations and to write his own models for final state production The design is a variant of a Chain of Responsibility An example would be the likely CMS scenario the combination of
78. re Engineering Standards for the development process The spiral or iter ative approach has been adopted User requirements were collected in the initial phase and problem domain decomposition object oriented methods and CASE tools were used for analysis and design This produced a clear hierarchical structure of sub domains linked by a uni directional flow of de pendencies This led to a software product which is modular and flexible a toolkit and in which the physics implementation is transparent and open to user validation of physics predictions It allows the user to understand cus tomize and extend the toolkit in all domains At the same time the modular architecture allows the user to load only needed components Chapter 3 Run 3 1 Design Philosophy The run category manages collections of events that share a common beam and detector implementation 3 2 Class Design e G4Run This class represents a run An object of this class is con structed and deleted by G4RunManager e G4RunManager the run controller class Users must register de tector construction physics list and primary generator action classes to it G4RunManager or a derived class must be a singleton e G4RunManagerKernel provides control of the Geant4 kernel This class is constructed by G4RunManager 3 3 Status of this chapter 28 06 05 under construction Chapter 4 Event 4 1 Design Philosophy In high energy physics the primary unit of an
79. require knowledge of the global objects instantiated By using static methods via a unique generator the randomness of a sequence of numbers is best assured Hence the use of a static generator has been introduced in the original design of HEPRandom as a project requirement in GEANT4 12 2 Class Design Analysis and design of the HEPRandom module have been achieved following the Booch Object Oriented methodology Some of the original design dia grams in Booch notation are reported below Fig 12 1 is a general picture of the static class diagram HepRandomEngine abstract class defining the interface for each Random engine Its pure virtual methods must be defined by its sub classes representing the concrete Random engines HepJamesRandom class inheriting from HepRandomEngine and defining a flat random number generator according to the algorithm described in F James Comp Phys Comm 60 1990 329 This class is instantiated by default as the default random engine DRand48Engine class inheriting from HepRandomEngine and defin ing a flat random number generator according to the drand48 and srand48 system functions from the C standard library RandEngine class inheriting from HepRandomEngine and defining a flat random number generator according to the rand and srand system functions from the C standard library RanluxEngine class inheriting from HepRandomEngine and defin ing a flat random number generator according to
80. stStepDolt k AEA gt oy GetContinuousStepLimit W A G4VRestDiscreteProcess rd b P AtRestDolt tC GAVContinuousProcess ZA Pa GetMeanLifeTime 7 AlongStepDolt gt gt G4VDiscreteProcess he GetMeanFreePath wm GetContinuousStepLimit f d GetMeanFreePath ges n b TS PostStepDolt DOS i PostStepDolt r zu ES MIS G4hEnergyLoss j j d AlongStepDol j TX KEN m e i PostStepDolt B Y a 1 L GetContinuousStepLimit tas f NE GetMeanFreePath N N 7 2 J p ee ae Neat N N N N G4eMultipleScattering Av n ESEN NM BN KER N ed Le fU SE Ge pment NE G4ComptonScattering y AlongStepDolt QAhlonisation G4eplusAnnihilation GaDecay G4Transportation Po tDol PostStepDolt e gt PostStepDolt P AtRestDolt fi Decaylt 1 GetContinuousStepLimit f GetMeanFreePath i GetContinuousStepLimit lt GetMeanFreePath a PostStepDolt GetMeanFreePath 1 AlongStepDoli s N TfrueGeomTransformation _ i GetMeanLifeTime GetLifeTime Vo SER V GetMeanFreePath l GetMeanFreePath 1 Figure 6 2 General Physics Processes 24 Chapter 7 Hits and Digitization 7 1 Design Philosophy In GEANT4 a hit is a snapshot of a physical interaction or an accumulation of int
81. t developer of GEANT4 wants to add entries of view parameters he should add fields and methods to G4ViewParameters 13 5 Status of this section 27 06 05 partially re organized and section on design philosophy added from Geant4 general paper by D H Wright 51 Chapter 14 Intercoms 14 1 Design Philosophy The intercoms category implements an expandable command interpreter which is the key mechanism in GEANT4 for realizing customizable and state dependent user interactions with all categories without being perturbed by the dependencies among classes The capturing of commands is handled by a C abstract class G4 UIsession Various concrete implementations of the command capturer are contained in the user interfaces category Taking into account the rapid evolution of graphical user interface GUI technology and consequent dependence on external facilities plural and extensible GUIs are offered Programmers need only know how to register the commands and parame ters appropriate to their problem domain no knowledge of GUI programming is required to allow an application to use them through one of the available GUIs The intercoms category also provides the virtual base classes e G4VVisManager e G4VGraphicsScene and e G4VGlobalFastSimulation Manager 14 2 Class Design e GAUlISession e GAUIBatch 52 e G4UICommand e G4UIparameter e G4UImessenger The object oriented design of the user interface rel
82. tDaughter lt lt const gt gt GetMaterial lt lt const gt gt GetName S const GetNoDaughters lt lt const gt gt GetSolid RemoveDaughter G4PVPlacement G4PVReplica G4PVPlacement G4PVReplica amp amp CheckAndSetParamete G4PVParameterised G4PVParameterised L fparam 0 G4VPVParameterisation S virtual ComputeDimensions J virtual ComputeMaterial S virtual ComputeSolid lt lt virtual gt gt ComputeTransforma Figure 20 2 Physical volumes 86 G4VoxelLimits from management AddLimit clipToLimits GetMaxExtent G4SolidStore GetMinExtent from management S inside IsLimited Soutcode lt lt static gt gt DeRegister G4LogicalVol lt lt static gt gt GetInstance ogicalVolume lt static gt gt Register from management A gt fName G4String b i lt lt const gt gt GetName G4VSolid from management Zfsolid fshapeName G4String 1 lt lt virtual gt gt CalculateExtent lt virtual gt gt Comput eDimensions lt lt virtual gt gt DistanceToIn lt lt virtual gt gt DistanceToOut S const GetName lt lt virtual gt gt Inside lt lt virtual gt gt SurfaceNormal G4CSGSolid
83. tedSting Decay i lt lt Purely Abs tract gt gt G4 VFragmertabon Function rGstLightConis 20 aR Sun eres Concrets G4OGSMFragnentsion P GtLund StingFragmertabon AG stLighhConsZ GtFemmanFragmentation gratwricewro Aj af G stL ghtCons20 Figure 18 8 Level 5 implementation framework of the hadronic category of GEANT4 string fragmentation aspect The use case of this level is that of a user or theoretical physicist wishing to understand the systematic effects involved in combining various fragmen tation functions with individual types of string fragmentation Note that this framework level is meeting the current state of the art making extensions and changes of interfaces in subsequent releases likely Requirements 1 Allow the selection of fragmentation function Design and interfaces A base class for fragmentation functions G4VFragmentation Function is provided It declares the GetLightConeZ interface 79 Framework functionality The design is a basic Strategy The class diagram is shown in Fig 18 8 At this point in time the usage of the G4VFragmentationFunction is not enforced by design but made available from the G4VStringFragmentation to an implementer of a concrete string decay G4VStringFragmentation provides a registering mechanism for the concrete fragmentation function It delegates the calculation of z of the hadron to split of the string to the concrete implementation Standardisa tion in this
84. the algorithm de scribed in F James Comp Phys Comm 60 1990 329 344 and orig inally implemented in FORTRAN 77 as part of the MATHLIB HEP library It provides 5 different luxury levels 0 4 RanecuEngine class inheriting from HepRandomEngine and defin ing a flat random number generator according to the algorithm RANECU originally written in FORTRAN 77 as part of the MATHLIB HEP li brary It uses a table of seeds which provides uncorrelated couples of seed values 43 e HepRandom the main class collecting all the methods defining the different random generators applied to HepRandomEngine It is a sin gleton class which all the distribution classes derive from This single ton is instantiated by default e RandFlat distribution class for flat random number generation It also provides methods to fill an array of flat random values given its size or shoot bits e RandExponential distribution class defining exponential random number distribution given a mean It also provides a method to fill an array of flat random values given its size e RandGauss distribution class defining Gauss random number dis tribution given a mean or specifying also a deviation It also provides a method to fill an array of flat random values given its size e RandBreit Wigner distribution class defining the Breit Wigner ran dom number distribution It also provides a method to fill an array of flat random values given its size
85. the class of objects which transform the hits deposited by particles into digitizations G4DigitizerManager the single object dispatching common mes sages to individual digitizers G4VDigi an abstract base class for all G4 digitizations This could be data as simple as a singe byte or as complex as an Ntuple G4DigiStructure digitizations are organized as a structure which could be anything between a single value and an Ntuple The object oriented design of the hit related classes is shown in the following class diagrams The diagrams are described in the Booch notation Fig 7 1 shows the general management of hit classes Fig 7 2 shows the OO design of user related hit classes Fig 7 3 shows the OO design of the readout geometry 26 G4VSensitiveDetector GAVHitsCollection These derived classes are just examples emi 4 Implementations should be done by drawAll ei lleeti r users accoring to their actual 3 endOfEvent k detector setups N getName j processHits x ul DESC CM EC ESSA rr os er calorimeterHitsColle gt Gavan n neons 7 emesen ae draw i tsCollection 4 Me J print EN Perik i P 2 RWrValOrder dVe 7 a 2 a ctor z N from RogueWave chamber j RE i MET chamber
86. tion in sensitive volumes for hits and digitization 5 1 Design Philosophy It is well known that the overall performance of a detector simulation de pends critically on the CPU time spent propagating the particle through one step The most important consideration in the object design of the track ing category is maintaining high execution speed in the GEANT4 simulation while utilizing the power of the object oriented approach An extreme approach to the particle tracking design would be to integrate all functionalities required for the propagation of a particle into a single class This design approach looks object oriented because a particle in the real world propagates by itself while interacting with the material surrounding it However in terms of data hiding which is one of the most important ingredients in the object oriented approach the design can be improved Combining all the necessary functionalities into a single class exposes all the data attributes to a large number of methods in the class This is basically equivalent to using a common block in Fortran Instead of the big class approach a hierarchical design was employed by GEANTA The hierarchical approach which includes inheritance and aggre gation enables large complex software systems to be designed in a structured way The simulation of a particle passing through matter is a complex task involving particles detector geometry physics interactions and hits in the
87. tope DumpTable Dump Table DumpTable End es nt Ue n p usce 2 2 pe N d theElements 1 thielsotopes 3 1 1 ina qi buc t G4Element gt G4ls Vector Z CURIE 7 748 0 N 2 daka vs A Pa Sg P d gt Pdl ha a y yt s RWTPtrVe ctor from RWTools he dro Chapter 12 Global Usage 12 1 Design Philosophy The global category covers the system of units constants numerics and random number handling It can be considered a place holder for gen eral purpose classes used by all categories defined in GEANT4 No back dependencies to other GEANT4 categories affect the global domain There are direct dependencies of the global category on external packages such as CLHEP STL and miscellaneous system utilities Within the management sub category are utility classes generally used within the GEANT4 kernel They are for the most part uncorrelated with one another and include G4 Allocator G4 Fast Vector G4 Reference CountedHandle G4Physics Vector G4LPhysicsFree Vector G4 Physics OrderedFree Vector G4 Timer G4UserLimits G4 Units Table A general description of these classes is given in section 3 2 of the GEANT4 User s Guide for Application Developers In applications where it is necessary to generate random numbers nor mally from the same engine in many different methods and parts of the 42 program it is highly desirable not to rely on or
88. ts runtime performance may be worthwhile To extend the functionality of the Geometry in this way a toolkit de veloper must write a small number of methods for the new solid We will document below these methods and their specifications Note that the imple mentation details for some methods are not a trivial matter these methods must provide the functionality of finding whether a point is inside a solid finding the intersection of a line with it and finding the distance to the solid along any direction However once the solid class has been created with all its specifications fulfilled it can be used like any GEANTA solid as it implements the abstract interface of G4VSolid Other additions can also potentially be achieved For example an ad vanced user could add a new way of creating physical volumes However be cause each type of volume has a corresponding navigator helper this would require to create a new Navigator as well To do this the user would have to inherit from G4Navigator and modify the new Navigator to handle this type of volumes This can certainly be done but will probably be made easier to achieve in the future versions of the GEANT4 toolkit 59 15 2 Adding a new type of Solid We list below the required methods for integrating a new type of solid in GEANT4 Note that GEANT4 s specifications for a solid pay significant at tention to what happens at points that are within a small distance tolerance kCar Toleran
89. virtual G4VisExtent GetExtent const virtual G4Polyhedron CreatePolyhedron const virtual G4NURBS CreateNURBS const virtual G4Polyhedron GetPolyhedron O const What these methods should do and how they should be implemented is described here void DescribeYourselfTo G4VGraphicsScene amp scene const This method is required in order to identify the solid to the graphics scene It is used for the purposes of double dispatch All implementations should be similar to the one for G4Box 58 void G4Box DescribeYourselfTo G4VGraphicsScene amp scene const scene AddSolid this The method G4VisExtent GetExtent const provides extent bounding box as a possible hint to the graphics view You must create it by finding a box that encloses your solid and returning a VisExtent that is created from this The G4VisExtent must presumably be given the minus x plus x minus y plus y minus z and plus z extents of this box For example a cylinder can say G4VisExtent G4Tubs GetExtent const i Define the sides of the box into which the G4Tubs instance return G4VisExtent fRMax fRMax fRMax fRMax fDz fDz J The method G4Po1yhedron CreatePolyhedron const is required by the visualisation system in order to create a realistic ren dering of your solid To create a G4Polyhedron for your solid consult G4Polyhedron While the method G4Polyhedron GetPolyhedron const is a smart
90. wise 56 G4ThreeVector SurfaceNormal const G4ThreeVector amp p Return the outwards pointing unit normal of the shape for the surface closest to the point at offset p G4double DistanceToIn const G4ThreeVector amp p Calculate distance to nearest surface of shape from an outside point p The distance can be an underestimate G4double DistanceToIn const G4ThreeVector amp p const G4ThreeVector amp v Return the distance along the normalised vector v to the shape from the point at offset p If there is no intersection return kInfinity The first intersection resulting from leaving a surface volume is discarded Hence this is tolerant of points on surface of shape G4double DistanceToOut const G4ThreeVector amp p Calculate distance to nearest surface of shape from an inside point The distance can be an underestimate G4double DistanceToOut const G4ThreeVector amp p const G4ThreeVector amp v const G4bool calcNorm false G4bool validNorm 0 G4ThreeVector n 0 Return distance along the normalised vector v to the shape from a point at an offset p inside or on the surface of the shape Intersections with surfaces when the point is not greater than kCarTolerance 2 from a surface must be ignored If calcNorm is true then it must also set validNorm to either e true if the solid lies entirely behind or on the exiting surface Then it must set n to the outwards normal vector the Magnitude of the vector is not
91. you will have then to inherit from it and modify these functions in your ModifiedNavigator to request the answers for your new physical volume type from the new helper class The Modified Navigator should delegate other cases to the GEANT4 s standard Navigator Replacing the Navigator Replacing the Navigator is another possible operation It is similar to extending the Navigator in that any types of physical volume that will be allowed must be handled by it The same functionality is required as described in the previous section However the amount of work is probably potentially larger if support for all the current types of physical volumes is required The Navigator utilises one helper class for each type of physical volume that exists These could also potentially be replaced allowing a simpler way to create a new navigation system 60 Chapter 16 Electromagnetic Fields 16 1 Creating a New Type of Field GEANT4 currently handles magnetic and electric fields and in future releases will handle combined electromagnetic fields Fields due to other forces not yet included in GEANTA can be provided by describing the new field and the force it exerts on a particle passing through it For the time being all fields must be time independent This restriction may be lifted in the future In order to accommodate a new type of field two classes must be created a field type and a class that determines the force The GEANT4 system must th

Geant4 User's Guide - For Toolkit Developers June 28, 2005

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